MBL WHOI
.
390
MAY M. JARVIS.
shape and arrangement ; these seem to indicate an erosion of the ridges and the papillae. In some, again, the ridges have worn away, leaving only the papillae, but the arrangement of these is as in the other cases. At the summit of each papilla, or at the center of each depressed area, is a minute foramen penetrating the wall of the test.
Fig. 7 shows the structure in ideal cross section. The whole interior is filled completely with foreign, calcareous substance, containing fragments of sponge spicules.
In no one specimen is the sculpturation preserved over the entire fossil, but a comparison of the different ones shows that the test in life, except just around the foramen, must have been so sculptured. The radial canals around the foramen are usually continued upwards as rows of minute depressions. Possibly such radial canals were not present in life, but produced by ero- sion of the exterior.
Measurements. — The largest specimens have a diameter of 25 x 31 mm. ; smaller ones from 9 to 18 mm. The large basal foramen measures from 4 to 7 mm. across.
These fossils present few good characteristics to enable one to decide what their nature was. But there is no resemblance, as Cragin had supposed, to Bryozoa, for even in a colonial ecto- proctous Bryozoan the cysts of the separate individuals are more or less cylindrical, and there is no sign at all of any such structures. Evidently the structure is that of a very thin shell or test, without prolongations into the interior, with a large opening at one end and rows of numerous minute foramina else- where upon the surface. This general appearance suggests that it is a gigantic monothalamnian Foraminifer that in the course of fossilizatioti has become infiltrated so as to be quite solid. Were it Bryozoan there should be present traces of skele- tal parts within the test.
BIOLOGICAL BULLETIN
OF THE
flDarine Biological Xaborator\>
WOODS HOLL, MASS.
Staff.
E. G. CONKLIN — The University of Pennsylvania. JACQUES LOEB — The University of California. T. H. MORGAN — Columbia University. W. M. WHEELER — American Museum of Natural
History, New York.
C. O. WHITMAN — The University of Chicago. E. B. WILSON — Columbia University.
Efcitor.
FRANK R. LILLIE — The University of Chicago.
VOLUME X.
WOODS HOLL, MASS. DECEMBER, 1905, TO MAY, 1906.
PRESS OF
•HE NEW ERA PRINTING COMPANY LAN CASTER, PA.
CONTENTS OF VOL X.
No. i. DECEMBER, 1905 PAGE
ADELE M. FIELDE : The Progressive Odor of Ants I
E. H. HARPER : Reactions to Light and Mechanical Stimuli in the EartJi-
u'orm Perichceta Bermudensis (Beddard) 17
LULU F. ALLABACH : Some Points Regarding the Behavior of Me-
fridiuw 35
No. 2. JANUARY, 1906
R. R. BENSLEY : An Examination of the Methods for the Microscopical Detection of Phosphorus Compounds other than Phosphates in the Tissues of Animals and Plants 49
J. F. McCLENDON : On the Locomotion of a Sea Anemone (Metridiitm
marginatuni) 66
H. H. NEWMAN: The Significance of Scute and Plate "Abnormalities"
in Chelonia 68
No. 3. FEBRUARY, 1906
H. H. NEWMAN: The Significance of Scute and Plate "Abnormalities"
in Chelonia 99
T. B. ROBERTSON: Note on the Influence of Surface -Evaporation upon
the Distribution of Infusoria 115
VERNON L. KELLOGG : Histogensis in Insect Development, and Cell
Specificity 1 20
E. A. ANDREWS : Ontogony of the Annulus Ventralis 122
No. 4. MARCH, 1906
O. C. GLASER : Correlation in tJie Development of Fasciolaria 139
CHARLES S. ROGERS: A Chameleon-like Change in Diemyctylus 165
A. C. EYCLESHYMER : The Growth and Regeneration of the Gills in the
Young Nee turns 171
W. L. TOWER : Observations on the Changes in the Hypodermis and Cuti-
cicla of Coleoptera During Ecdysis 176
iii
iv CONTENTS
No. 5. APRIL, 1906
PAGE
ESTHER F. BYRNES : Two Transitional Stages in the Development of
Cyclops signatits, var. coronatus 193
T. H. MORGAN : The Male and Female Eggs of Phylloxerans of the
Hickories 201
CHAS. W. HARGITT : The Organization and Early Development of the
Egg of Clava leptostyla Ag. 207
PHILIP B. HADLEY : Regarding the Rate of Growth of the American
Lobster 233
T. B. ROBERTSON : Note on the Influence of Temperature upon the Rate
of the Heart-beat in a Crustacean ( Ceriodaphnia) 242
L. B. SEELY : Two Distomes 249
No. 6. MAY, 1906
INEZ L. WHIPPLE : The Ypsiloid Apparatus of Urodeles 255
FRANCIS B. SUMNER : The Osmotic Relations Between Fishes and their
Surrounding Medium (Preliminary Note} 298
Vol. X. December, 1905. No. i
BIOLOGICAL BULLETIN
THE PROGRESSIVE ODOR OF ANTS.
ADELE M. FIELDE.
I. STATEMENT OF HYPOTHESES BASED ON RECENT AND FORMER EXPERIMENTS.
1. The Specific Odor. — The mother-ant transmits to her off- spring the distinctive odor which is identical for ants of all ages and of both sexes within the species. This odor is appreciated among ants by organs near the proximal end of the funicle.1
2. Progressive Odor. — Female ants, including queens and workers, have, besides their specific odor, an odor which may be termed progressive. Queens of different lineage have different progressive odors. In a queen this odor is either unchanging or changes very slowly, and it is similar to that of her newly- hatched female offspring.
a. As worker-ants advance in age their progressive odor intensifies or changes to such a degree that they may be said to attain a new odor every two or three months. This progressive odor is appreciated among ants by organs in the penultimate joint of the funicle.2
b. Male ants have no progressive odor unless it be super- ficially incurred through association with workers ; but the male carries latent in his spermatozoa the progressive odor of his mother. In other words the progressive odor is always recessive in the male ant.
c. The progressive odor of each new generation of females is
1 "Artificial Mixed Nests of Ants," A. M. Fielde, BIOLOGICAL BULLETIN, Vol. V., No. 6, November, 1903, p. 320.
2 "Farther Study of an Ant," A. M. Fielde, Proceedings of the Academy of +\ 'at nra I Sciences, November, 1901, p. 531.
2 ADELE M. FIELDE.
determined by the odor of the mother latent in her egg, and the odor of the father's mother latent in the spermatozoon. The progressive odor therefore changes in each generation of females.
d. The progressive odor manifest in female ants is the cause of the separation of ants of the same species into hostile colonies, and is of great advantage to the ants in their individual and their communal life.
3. The Incurred Odor. — An ant may incur from its associates an odor which is not inherent in itself, and which may be removed by washing. It may be transferred from ant to ant through air or through water. It arises from the substances that give the specific odor and the progressive odor and that create the nest-aura.
II. RECENT EXPERIMENTS WITH THE PROGENY OF A SINGLE QUEEN, COMPONOTUS PENNSYLVANICUS.
In 1901 I found that the odor of working-ants of Stcnainma fulvmn piccuin changes with their age,1 forty days being the mini- mum of time in which there occurs a change so great as to effect the behavior of ants of the same colony toward one another at their first meeting.
In 1902 my further experiments indicated that a cause 2 for the hostility of one colony toward another of the same species and variety is a difference in odor coincident with difference in the age of the colonies.
In 1904 my observations on several species of ants,3 represent- ing three subfamilies, gave further evidence of their change of odor with advance of age, and indicated that the odor of the queen is unchanging, or that her odor changes much more slowly than does that of the workers.
1 have now had under observation for more than two years a colony of Caniponotus pcnnsylvaniats, in which the assertion of a
1('A Study of an Ant," Proceedings of the Academy of Natural Sciences of Philadelphia, July, 1901, p. 449.
2 " Notes on an Ant," Proceedings of the Academy of Natural Sciences of Phila- delphia, September, 1902, p. 609 ; " Cause of Feud Between Ants of the Same Species," BIOLOGICAL BULLETIN, Vol. V., No. 6, November, 1903, p. 328.
3" Power of Recognition Among Ants," BIOLOGICAL BULLETIN, Vol. VII., No. 5, October, 1904, p. 244.
THE PROGRESSIVE ODOR OF ANTS. 3
progressive odor in the workers is definite and indisputable, the five successive broods included in the experiment being the issue of one queen.
The N Queen.- -This queen was captured on Nonamesset Island, July 28, 1903. She was then deflated and was probably the mother of the hundred workers seen in her wild nest, and also of the ants that afterwards hatched from the many cocoons brought with her to the laboratory. She remained under my care and, unless another is indicated, she is the queen referred to in the herein recorded experiments.
The Ni Group of Workers. — Some of the captured workers were transferred to Dr. Irving A. Field, and they remained segre- gated in his care, usually at Harvard University, until the time of the experiment in which they appear. As no other than male offspring had appeared in this group during the two years of its separation from the queen mother, the workers composing it in August, 1905,, were certainly acquainted with the queen pre- vious to her capture in July, 1903. Of the age of these workers of course nothing more was known than that it exceeded two years.
On August 6, 1905, I introduced into this nest,1 where there were six major and five minor workers and about thirty larvae from their own eggs, the queen-mother from whom these eleven workers had been separated for two years. The queen showed instant hostility, seized a major worker by one of its mandibles, braced herself on the sponge and held her prisoner there during the ensuing seven hours. All the other workers, sometimes six at a time, examined the queen meanwhile. They patted her with their antennae, nabbed her gently, and licked her back and legs. Two of them, touching her body with their antennae, appeared to dance for joy, shuffling their feet with great rapidity during several consecutive minutes. The queen then began to drag the worker that she had seized, and upon my releasing the latter, took a position near the larvae-pile, as if to claim her incipient grand- sons as her exclusive property, opening her mandibles at every worker who approached. Then followed a most curious and pro-
1 All the artificial nests referred to in this paper were of the Fielde pattern. See "Portable Ant-Nests," BIOLOGICAL BULLETIN, Vol. VII., No. 4, September, 1504.
4 ADELE M. FIELDE.
longed effort on the part of the workers to placate the queen- mother. They surrounded her at all times, offering her regurgi- tated food. Whichever way she turned, there stood a humble servant with a proffered mouthful of pabulum. As many as seven workers simultaneously offered nourishment to her. Every worker of the eleven seemed bent upon wooing and winning her, and she was not for a moment left without attention. These efforts were unceasingly continued, and were meeting with a fair degree of success, when I removed the queen on the following
morning.
This experiment showed that the workers all recognized the odor of their queen after two years of separation from it, and that the segregated workers had during the same interval acquired an odor unfamiliar to the queen, who had meanwhile met none of her daughters who were over fifteen months old. It also showed that major workers, having in this species nearly the same form and sometimes nearly the same bulk as has the queen, are like minor workers in having a progressive odor.
On August 7 I introduced into this Ni group a marked major and a marked minor worker, daughters of the N queen, but many months younger than any of the ants in this group. The visitors were received with signs of curiosity, but with perfect amiability, though no younger sisters had been encountered within two years by these Ni ants. The odor of the younger sisters was perfectly recognized by the eleven residents, and I removed the former.
I then introduced a young winged queen of the same species, Camponotns pennsylvanicus, but of an alien colony. The resident ants attacked her instantly and with exceeding virulence. In an instant she lost an antenna, one worker was pulling out her remaining antenna, and three others were dragging her by her legs. The scrimmage was fierce, and before I removed the in- truder four of the residents had received injuries that resulted in their deaths. The residents had given to the alien queen a reception strongly contrasted with that accorded to their own queen-mother ; while the havoc wrought by the alien queen indicated that, if unable to escape from the nest, she might have destroyed all the workers and have remained a fostering mother to their larvae.
THE PROGRESSIVE ODOR OF ANTS. 5
T/ic JV2 group. — During the first week in August, 1903, the queen deposited about a hundred eggs, and from these were reared five minor workers, denoted here as the N2 ants. These workers hatched between April 24 and May 10, 1904, and were therefore some fifteen months old at the time of the experiment here recorded. These workers had never met other ants than those of their own segregated group, and were therefore unac- quainted with the odor of ants in any wise unlike themselves. They had never lived with the queen, had laid no eggs, and had the care of no young. On July 16, 1905, I put these ants into a new and very small nest where I had isolated the queen-mother without young. The five workers were wholly at ease with the queen, and hastened to evince their devotion in ant fashion; but the queen opened her jaws whenever they approached her, and was somewhat querulous in her behavior during the ensuing two days. The queen had lived during the previous five months with daughters, all minor ants, less than five months old, and her be- havior indicated a difference in the odor of her younger and her older daughters. Her memory was manifestly less tenacious than that of the workers, who, on their part recognized in their queen the odor that had been their own in their infancy, fourteen months earlier.
The Nj group. — This group consisted of two major workers hatched in July, 1904, and four of their younger sisters, minor workers, over five months and less than a year old, all the issue of the N queen. The two majors were acquainted with sisters older than themselves, while the minors knew no sister older than these two majors. The members of this group had all lived with the queen, and had been separated from her and living in segregation since February 14, 1905. They had deposited no eggs, and they had the care of a few introduced larvae. On July 1 8, 1905, I introduced into this group a sister nine months older than the oldest in the group. The majors, who had had acquaint- ance with sisters much older than themselves, did not attack the newcomer at all, while every one of the minors, never having met a sister so old as was the visitor, attacked, dragged and finally killed her.
It appeared that the behavior of the two major workers was
0 ADELE M. FIELDE.
dictated by memory, while that of the four minor workers was an effect of hostility created by the presentation of an unfamiliar odor. The major workers were either wanting in compassion, or else they lacked means of communicating with their younger sisters, for although they were each double the size of any minor ant in the group, they did not interfere in behalf of the victim.
The Nj. Group. - - The queen was transferred without eggs or young to a new nest on July 14, 1904. She laid no eggs there- after until December, 1904, and from the eggs then deposited the five minor workers constituting the N4 group were hatched between February 19 and March 23, 1905. These workers were therefore four or five months old at the time of the experiment. On July 16, 1905, I removed the queen from the nest, leaving the five workers in charge of twenty larvae, the issue of the queen's December eggs. Into this group of five minors, who had never met older sisters, I introduced one of the majors from group IS 3, now just a year old, and twice or thrice the bulk of any of the five residents. The introduced ant was instantly and violently attacked by three residents. This attack indicates that the major, like the minor ants, like in shape and size as they are to the queen, change their odor with advance in age, as do minor workers.
Having removed this visitor, I introduced a marked large minor worker, fourteen months older than the residents, a sister of theirs, hatched from eggs deposited by the queen in August, 1903. This visitor was likewise violently attacked, every one of the five residents manifesting hostility to her, and the next day I found her mangled body on their rubbish pile.
The N$ Group. — This group consisted of two minor workers, the issue of the queen's December eggs, sequestered in their cocoons and hatched on September 8, 1905. They were at once placed in segregation in a new nest, with a few larvae and cocoons from their mother's eggs. Ten days later these ants drove away from their pile of young any member of the N4 group of sisters six months older than themselves.
In these experiments it appears that it is the age of the work- ers, not the age of the queen at the time when she deposits the eggs from which the workers issue, that determines at any date
THE PROGRESSIVE ODOR OF ANTS. 7
their progressive odor. All the ants engaged in this last men- tioned experiment were certainly the issue of the eggs laid by the queen early in December, 1904. That there is similar progress in odor among ants of the same age and species is indicated by an immediate and amicable association of ants that are reunited after a period of separation so long as two years.1
Whether two mutually hostile groups could be created from among the worker-progeny of a single queen would depend on power of memory in the older workers. By segregating from the pupa-stage the broods of different summers, it would be found that the younger sisters would always be hostile to the older sisters, because the older sisters would present an unfamiliar odor to the younger. The hostility of the older sisters toward the younger would be nullified by their memory of the odors by which they had themselves been characterized at earlier periods in their own lives. If the younger sisters bore an odor which the older sisters, through the lapse of many years, should have forgotten, then the hostility would become mutual. It is certain that worker-ants can remember for years an odor with which they have once become familiar, and it is probable that they remember such odors as long as they live.
When ants of different groups meet amicably, either the mem- bers of these groups have the same odor, or else they have at some time in their lives been familiar with ants bearing the pre- sented odor. If one group recognizes a familiar odor, while the other group discerns a strange odor, then thos'e finding them- selves among strangers will try to escape, or will make attack. There is no love at first sight between ants of different odors.
III. THE ODOR AND THE SENSE OF SMELL IN MALE ANTS.
Male ants apparently bear a specific odor, beside the odor that may be incurred during their residence with nurses in the home nest. I have introduced males of different species into the nests of Steitamma fu/vni/i, Cremastogaster lineolata, Mynnica ritbra, Formica sanguinea, Formica Schaufnssi, Camponotus pennsyl-
1 " A Cause of Feud Between Ants of the Same Species Living in Different Com- munities," A. M. Fields, BIOLOGICAL BULLETIN, Vol. V. , No. 6, November, 1903,
P-
8 ADELE M. FIELDE.
vamcns, Camponotus pictus, Camponotus americanus, Lasius latipes, and Lasius umbratns, and all these males have invariably been killed within a day or two. If hybridization is to be effected among ants it will be necessary to cause the males and females to become acquainted with one another within a few hours after hatching. When hatched in the same nest, males of Sten- ammafiilvum pursue queens of Cremastogaster liucolata with the same ardor that they show in pursuing queens of their own species. In my mixed nests the failure of individuals of these two genera to mate was manifestly due to physical and not to psychic incompatibility.
In the summer of 1905 I had material in my stock of ants for experiments giving evidence that the male ant has at hatching the specific odor of his virgin worker-mother. My E mixed nest consisted of workers of Cainponotus pictus, Formica ncoga- gates, Formica subscricea, and Stcnanima fulvinn, all hatched during the last week of July, 1904, and kept in the same nest until the first day of January, 1905, when the Stenammas were segregated apart. They remained in segregation until August 22, 1905, when I put into their small nest, where there were ten workers and a few eggs, a fine male Camponotus pictus, the offspring of a virgin worker-mother who had shared the nest of these Stenammas until she was five months old. This young male was received by the resident Stenammas with evident pleas- ure. They licked him, regurgitated food to him, and rode on his back. He continued to live happily with them for many days. He bore a familiar specific odor, although hatched among segre- gated workers of his species, eight months older than any that these Sfenammas had known ; and this familiar odor made him welcome. His fate was in strong contrast to that of some of his brothers or cousins introduced into another nest. At the time of these experiments I had also a nest, marked D, of eleven Stenamma fuhnun workers, that had hatched in a mixed nest during the last half of August, 1903, and had lived for several months with Camponotus pennsylvanicns, and Formica subsericea, but had never met a Camponotus pictns. These eleven Stenammas had lived in segregation since July 17, 1904, and were destitute of young, when on August 22, 1905, I introduced into their nest
THE PROGRESSIVE ODOR OF ANTS. 9
a newly hatched Cainponotus pictJis male, the offspring of a virgin worker, a brother or cousin of the one in the E nest above mentioned. These ants of the D nest at once began to harry him, and although he was eleven millimeters long and very sturdy, while none of the Stenammas were more than five milli- meters in length, they harried his life out within two days. Repe- titions of this experiment gave similar results in every case.
The eggs from which these Cainponotus pictns males were produced were deposited by their virgin worker-mothers in May, 1905, five months after the said mothers were separated from the Stenammas that the said mothers had lived with during the first five months of their lives. It therefore appears that the male progeny of virgin workers have not the progressive odor which characterized their mothers. The males have, however, a specific odor, an odor recognized by the ants through certain joints of the antennae, and this odor is doubtless the stimulus calling forth the exceeding care given by the workers to young males with whose specific odor they are familiar.
On August 26 I put into each nest, the E and the D nests above described, two males of Stenamma fnlvnni. These males, the first of their species ever encountered by these workers, wery treated alike in the two nests. They were so eagerly grasped be several residents at once that it seemed as if they must lose their lives through the determined efforts of the workers to retain them. They were not left free for several hours ; but so judi- cious were their virgin captors that no injury was done to the captives, and they lived in health and honor many days in these nests. In the E nest the Camponotns pictns male continued to be their associate.1 In both the E and the D nests newly hatched
1 A dealated queen Camoponolus pictus captured alone in the open on July 5, w kept in isolation till August 15, 1905, when she received amicably into her small artificial nest two young males of her species, the offspring of virgin worker ants. She licked them, regurgitated food to them, and during the several days that they remained under my observation, remained in close companionship with them. Later on this queen also received in amiable fashion the virgin mothers of these males, the worker-mothers having been kept by me in segregation during their whole lives. As this queen was captured near the spot in which the workers had their origin a year earlier, these ants may all have been of one colony. This queen killed young males of Formica argentata and Stenamma fitlvum introduced into her nest.
IO ADELE M. FIELDE.
Stenamma workers, from the same colony as were these males, were immediately killed.
Since the males avoid, or are indifferent to, ants of other spe- cies than their own, unless hatched among such species in arti- ficial nests, it appears probable that they discern the specific odor of other ants. But they probably lack the sub-nose that per- ceives the progessive odor of workers. Male ants of various species placed under observation in one of my artificial nests, grouped themselves according to species, but did not quarrel with males of species unlike their own. I infer that the only inherent odor of males is that of their species ; but that they are the medium through which the progressive odor of their female progenitors is transmitted to the egg that produces a female, the progressive odor being latent in the males and reappearing in their female descendants. Only the egg receiving a spermato- zoon would produce a female, and this female would be endowed with her paternal grandmother's tendencies in progressive odor, the progressive odor thus manifesting itself only in the female line of descent. The fact that the worker progeny of a queen, sequestered from the pupa stage, will receive their queen-mother or the queen-mother's sister with equal pleasure, indicates simi- larity of odor in the product of the same queen's impregnated
eggs.
I venture to predict that there will be found in female ants secretory glands or organs that are wanting or are rudimentary in the male, and that these organs are the producers of the pro- pressive odor. There must be in both males and females secre- tory glands or organs producing the specific odor which is com- mon to both sexes. These diverse organs might be identified through the possession of both sets by the female and of a single set in the male. It is also probable that the male lacks the glands that secrete the scent whereby the female lays down her individual path from the nest, and he may also lack the sub-nose which discerns this path-scent. The male seems to be unable to lay a path, and, in a change of domicile by the colony, he is car- ried bodily by the females to the new nest. It is through his appreciation of the specific odor and his lack of perception of the
THE PROGRESSIVE ODOR OF ANTS. I I
progressive odor that the male is best fitted for his distinctive office in the ant world.
IV. THE PROGRESSIVE ODOR OF QUEEN ANTS.
The change in the inherent, transmissible, progressive odor in a line of queens is probably slow and cumulative, but that such a change occurs is evidenced by the behavior of any segregated group of Stcnaunna fithnui workers, a species in which the queens generally remain in the colony in which they are pro- duced. When workers from such a colony are segregated from the pupa-stage upward, it becomes difficult to find, in the wild nest, any queen that these segregated workers will accept as their own. In this species, I have reared worker-offspring from queens that were sequestered from all males except those of their own colony,1 and these workers willingly associated with their worker- cousins. That the change of odor is but slight in a single gene- ration is also shown by the fact that the worker-daughters of a queen, after having been segregated from their pupa-stage upward, and with no criterion of odor save that of their own bodies, will affiliate with their queen-mother at a first meeting, though they always examine her with exceeding care before rendering com- plete homage.
The gradual change in odor, through the introduction of the male element, from generation to generation, may be crudely re- presented by the use of letters as symbols of the odor of queens of the same species and variety.
The Roman numerals at the left denote successive generations of mated queens.
The letter a is used as a symbol of the odor characterizing two sister queens ; the other letters as symbols of the odor inherited from the paternal grandmother.
I. a, I. a,
II. rt + 3, II. a-\-l,
HI. a + b + c, III. a + l+m,
IV. a+b + c + d, IV. a + l+m + n,
V. a + b -f c -f d-\- e, V. a -+ I -f m + « + o, etc. etc.
1 " Notes on an Ant," Proceedings of the Academy of Natural Sciences of Phila- delphia, December, 1902, p. 605.
12 ADELE M. FIELDE.
The female descendants of sister queens would thus become more unlike in odor with every generation.
An odor providing the means of recognizing a maternal ances- tor, or another descendant of that ancestor, may be dominant through more than one generation of females.
The fact that worker ants who have never met any queen will as joyfully associate with their queen-mother's sister as with their own mother, indicates that sister-queens have the same odor after mating that they had before mating, and that the first divergence in odor becomes apparent to the ants only in the offspring of sister-queens that mated with males capable of imparting unlike odors to their respective progeny. The worker ants, having attained the distinctive progressive odor characterizing their mothers' worker- offspring for the current year, may produce males who will each impart to his progeny the distinctive odor borne by all the female issue of the queen with whom he mates. Each generation in the line of queens would then depart farther from the odor of the queen ancestor, and we should find, as we do, colonies in which all the female inhabitants are inimical to all the female inhabitants of another colony. There would also be produced, as in colonies of Stenammafulvum, where queens mate within the nest and remain to increase its population, the phe- nomenon of callows that, if segregated from the pupa-stage, refuse to affiliate with queens from the nest in which were depos- ited the eggs from which these callows issued.
During several years I have been interested in ascertaining whether adult, queenless workers would willingly accept a queen who was indisputably of another colony of their own species, and among many experiments I have never seen such an acceptance. If forced into association, escape of either party being made im- possible, the workers may after a longer or shorter interval live peaceably with the alien queen, as they also may do with alien workers. But such forced alliances do not result in normal pros- perity, even when a whole year is allowed for the cementing of friendship. So exacting are the ants concerning adherence to their standard of odor that they prefer a queenless state to the presence of an unknown ant-oclor. Observations made by me in the summer of 1905 accord with my earlier ones. Eleven
THE PROGRESSIVE ODOR OF ANTS. 13
workers of Stenamma fulvum piccuin had been inmates of one of my mixed nests, with Camponotus pennsylvanicus and Formica subscricca, all hatched between August 14 and September 3, 1903. The Stcnammcts had been removed from the mixed nest, and kept in segregation since June 23, 1904, and had never met a queen. On August 13, 1905, I introduced into this nest a young, winged queen of the same variety as these workers, on the twenty-fourth day after I had isolated her to ensure her freedom from incurred odor. The queen fled from the group of workers and constantly tried to escape. She was attacked whenever I forced her into the group of workers, and was caught and killed by them on the ninth day of her sojourn. A dealated queen intro- duced later, from the wild colony to which these workers origi- nally belonged, was also killed by them.
Since ants possess so discriminating a sense of smell, and are so exacting concerning an adherence to the criterion established for their nest, and since even those ants who have had an ex- tended experience in ant-odors, and who have been queenless for two years, refuse to affiliate with a queen of an alien odor though of their own variety, we may hardly expect that they will volun- tarily associate with queens of another species. During the sum- mer of 1905 I introduced queens of other species into segregated, queenless groups of adult Stenamma fulvum^ of Formica ncoga- gatcs and of Formica Schaufussi, that had had their sense of smell highly educated by long association with workers of two or three different species of ants, but in every case the introduced queen was killed within a few days, in spite of her constant efforts to keep aloof from the workers.
In no species of ant have I found workers that would tolerate the presence of any queen of unfamiliar odor, nor any queen that would willingly remain among workers of unfamiliar odor. Although all species of ants have not been thus tested we may well assume that what is shown to be a fundamental trait in a few species will manifest itself in all species of the tribe.
14 ADELE M. FIELDE.
V. EFFECTS OF THE PROGRESSIVE ODOR IN THE COMMUNAL
LIFE OF ANTS.
Since the queen is ordinarily the earliest occupant of the ant- nest, and since her callow young have the same odor as herself, the odor of her earliest nest must at first be the same as is that of the queen. Probably this odor is at all times dominant in the permanent nest ; but as the progressive odor of the workers is gradually added thereto, the nest-aura would be thereby modi- fied. The change in the nest-aura, cumulative with the age of the colony and the increase of the inmates, would be so gradual that all habitants of the nest would at all times find it familiar and therefore congenial. The greater dominance of the queen's odor in the earlier nest may be the cause of the persistence with which many workers cling or return to the old habitation even after the majority of the colony has for sound reason removed to a new abode.
It appears probable also that diffused ant-odor is in direct ratio to bulk of ant-body, and that a cause of the common activity of workers in adding the lesser to the larger pile of brood, some- times even against the inhibitory effects of light, is due to the more manifest odor of the larger pile.
I have at different times during several years observed in my artificial nests a most curious phenomenon among ants that had long lived amicably together. Several or many workers were seen standing around one ant as if holding a court of inquiry con- cerning this associate. Sometimes the associate is proscribed, sometimes rent limb from limb. This extraordinary behavior is probably due to the victim having attained a progressive odor that is obnoxious to many other inmates of the nest because unknown to them. This might happen to an aged ant whose horde of com- panions were all young. It might also happen that in prowling for food, or in raids made on the nests of aliens, the worker ants would bring in alien young for food, and that this much licked and tended young would incur the progressive odor of the nurses. At a later period the introduced ant might produce a progres- sive odor unlike that of the multitude inhabiting the nest, and it would therefore be doomed to destruction. Ostracisms or violent
THE PROGRESSIVE ODOR OF ANTS. I 5
deaths, such as sometimes occur in nests where amity has long prevailed, are probably to be explained by the attainment by some of the inmates of a new and therefore an alarming progressive odor.
There may be seen among ants of the same variety, and even in the same individual, all degrees of attraction and repulsion towards other ants at a first meeting with them. Such manifes- tations range all the way from cuddling, caressing, cherishing de- votion through indifference and inattention, distrust, suspicion, animosity and enduring, ferocious enmity. The inciting cause is doubtless the progressive odor of the visitor, and the prac- tical end is the preservation of the chemical standard of the nest.
Whatever the action of the ants, it is always more obvious when there are numerous young in the nests, and when the nest- aura is well established.
During five years of fairly constant study of ants I have seen no evidence that their antennae are the organs of any other sense than the chemical sense, and I am convinced that any statement concerning the behavior of ants may well be distrusted if it ignore the dominance of the olfactory sense over the conduct of the ant, the ant's almost inconceivable minuteness of discrimination in odors, or the ant's marvelous memory of odors that have been encountered. Only when ants are segregated from the pupa- stage, and full record kept of every experience of theirs in meet- ing other ants, can the investigator truthfully declare that ants behave in a certain manner in the presence of other ants. More- over, as every ant acts on personal experience and individual memory, the ants should be considered singly as well as in groups and communities, when a theory of their behavior is to be enunciated. But when the total history of an ant is known, the investigator may accurately predict the behavior of that ant toward other ants. There is ex-ceeding uniformity of behavior among ants having an identical history.
The progressive odor of the worker ants is manifestly an ad- vantage in their communal life, since it furnishes the means whereby every ant can recognize its home and its fellow-citizens, avoiding nests and communities other than its own. The uses of this odor within the colony may also be numerous, and it may determine the distribution of labor in the ant community.
1 6 ADELE M. F1ELDE.
Through the male element, it probably differentiates the odor of queens of the same species, enabling the workers to find, to defend, and to cherish their own queen.
It differentiates ants otherwise alike ; determines their distribu- tion in separate communities ; dictates the behavior of members of one colony toward those of another colony, and in connection with an acute sense of smell and a powerful memory, is a domi- nant factor in the life of the individual ant and in the structure of the ant-colony.
REACTIONS TO LIGHT AND MECHANICAL STIMULI
IN THE EARTHWORM PERICH/ETA BER-
MUDENSIS (BEDDARD).
E. H. HARPER.
Recent work concerning the behavior of earthworms has related chiefly to their reactions to light. Since the contributions of Hofmeister and Darwin, and that of Hesse ('96) there have been a group of recent papers by Parker and Arkin, Miss Smith, Adams and Holmes, which have been devoted chiefly to the directive influence of light. In the present state of the discussion of this subject the current theory of tropisms has been called in question, according to which the earthworm is oriented directly by light. Holmes has shown that light induces a general state of activity leading to random movements of which those toward the light are checked and those away from it continued, this resulting in final orientation.
This paper aims to show that random movements are a feature of less strong light, tending to disappear with the increase of intensity, and are replaced by direct orientation in very strong light. It is also shown experimentally that the earthworm is more sensitive in the extended than in the contracted state, and that this has an important bearing upon the production of random movements. The explanation given of this is that when extended the sensitive elements of the skin are expanded over a greater surface. This is shown to have a bearing upon the production of random movements as follows : Locomotion consists of a succes- sion of extensions and contractions and as each extension begins in a state of lower sensibility the anterior end may be projected toward the light, only to be checked when its increase of sensi- bility with extension makes the stimulus appreciated. Movements away from the light are not so checked. In stronger light the sensibility of the worm when contracted is sufficient to suppress movements toward the light at the outset. In such light the worm appears to be orientated without trial movements. It is important that the worms be kept in the dark before all experi-
17
1 8 E. H. HARPER.
ments, as their discrimination diminishes and random movements begin again when this is the case.
It is shown that the reactions which are typical of the life in the burrow are more definite and controlled by weaker stimuli than reactions in the open, and this may be expressed by saying that the earthworm's organization is more highly adapted for life in the burrow. Reactions in the axial direction are definite and more sensitive to stimuli than lateral movements in response to light.
The genus Pcrichceta is noted for its agility, and of its special reactions the leaping movements are the most notable.
DESCRIPTION OF THE SPECIES.
Perichata, the eel- worm, as it is called by gardeners, is an exotic genus of earthworms which is said to be quite commonly established in greenhouses in the old world, and also in gardens in parts of France, where they have been introduced, it is said, from the east. The only mention of Pcrichceta having been found in this country, that has come under the writer's notice, is that of Garman, who reported a species of Pcrichatta as becom- ing established in greenhouses in Urbana, 111. The writer found Pcrichceta bermudensis (Beddard) in a greenhouse in Evanston, 111. In suitable conditions of soil these worms flourish in great abundance.
The genus Pcricliceta is noted for its activity. The squirming movements which have given it its name of eel-worm are a strik- ing exhibition of agility. This sort of movement is not confined to Pericliceta, but is developed in the genus to an extent not found elsewhere. By alternate contractions of the longitudinal muscle bands it makes a series of leaps, by which it may waltz about for quite a distance. It reacts in this way when handled or disturbed, as when uncovered from its burrow.
The worms are of rather large size. They are found often measuring nine inches in lengh when killed fully extended. They are rather pointed at both ends. The continuous circles of setae on each segment give the name to the family. The clitel- lum is a complete band or girdle encircling segments 14—16. A large pair of spermiducal glands shine through the opalescent
REACTIONS TO LIGHT IN THE EARTHWORM. 19
skin behind the clitellum, making a conspicuous mark. The dorsal pores are very prominent, exuding an abundant yellowish mucus. The everted buccal cavity is used as a proboscis, and is thrust out constantly in its feeling movements. The blood vessels are prominent, shining distinctly through the skin. The very numerous, minute, diffuse nephridia are a feature which, along with the continuous circles of setae, have caused consider- able discussion as to whether these conditions are primitive for earthworms or secondarily derived.
THE THEORY OF TROPISMS.
The orientations to light and other stimuli, which are among the most striking phenomena in the behavior of the lower ani- mals, have received various explanations. After the first anthro- pomorphic explanations of these movements, based upon likes and dislikes, there came an apparent revolution of ideas bringing in explanations of seemingly great simplicity. As the physiology of plants, particularly of the higher plants, had made consider- able progress towards a solid physico-chemical basis, there was a transference of conceptions based upon plant physiology to the realm of animal behavior and the orientations of the lower animals were illuminated by analogies drawn from plants. For example, we find the assertion of identity between heliotropic phenomena in plants and animals. The mechanism of the tropism was not a reflex according to this conception, but was a unique form of movement to be added to the classification of animal movements into reflex, instinctive and voluntary.
The current theory of phototropic or -tactic phenomena as ap- plied, for example, to the earthworm, was that when light strikes one side of the animal so as to cause unequal stimulation of the two sides, it changes the tone of the muscles on the side affected. The muscles of one side are thus either relaxed or their tension is increased according as the animal happens to be positively or negatively phototropic. It is bent away from or toward the source of stimulation by the direct action of the environment upon the protoplasm. The tropism is accordingly regarded as a peculiar kind of forced movement, dependent upon the chemical nature of the protoplasm.
2O E. H. HARPER.
Jennings has shown in the case of the Protozoa and also the Rotifera that the tropism theory gives an untrue explanation of the mechanism of orientation. These animals are not directly swerved away from or toward the source of stimulation, but they have their peculiar methods of reaction and orientation in the direction of the stimuli is effected by a sort of " trial and error "
method.
REACTIONS OF EARTHWORMS TO LIGHT.
Since Darwin's account of the habits of earthworms there has been a series of papers devoted chiefly to the directive action of light upon these forms. Parker and Arkin, Miss Smith, Adams and Holmes have studied the reactions of earthworms crawling over surfaces, exposed to light stimulation from one side.
Parker and Arkin observed the head movements of worms placed at right angles to the direction of the light and determined that 65 per cent, of the movements were indifferent, /. i\, straight ahead, 30 per cent, were away from the light and 4 per cent, toward it. They regarded the various head movements in differ- ent directions as due to a variety of chiefly undefined causes in addition to light and since 4 per cent, were toward the light they assume that as many of the negative responses would be due to other causes than light. So subtracting 4 per cent, from 30 per cent, the remaining 26 per cent, they regard as the measure of the negative phototactic response. Adams showed in addition that the earthworm is positive to very weak light.
The observers mentioned did not consider the question of the mechanism of orientation. Holmes takes up the current tropism theory and questions its explanation of the mechanism of orien- tation for these animals. He shows that the various extension movements appear to be of a simply random character, due to a general stimulation by light. The way in which orientation is effected he describes as follows. Movements that are toward the light are checked and the animal draws back and usually moves in the opposite direction. Movements away from the light do not lead to further stimulation and so are prolonged farther, and as a final result of such random movements, the worm gets into the direction of the rays, in which position the stimulation of the sensitive anterior end is least, and it then continues to move
REACTIONS TO LIGHT IN THE EARTHWORM. 21
straight ahead. Any swerving from this path leads to an increase of stimulation and hence is corrected. Holmes regards none of the movements as forced by light. All are random in direction but certain favorable ones are followed up and unfavorable ones checked by the increase of stimulation resulting from them.
Holmes proposes his theory of the " selection of random move- ments " only as one factor in phototaxis, not wishing to exclude the possibility of a slight amount of directive influence in the light. His reason for so doing is based on the observation of himself and the other experimenters alluded to that there is an excess of negative turnings over positive ones. Of course if the movements of the animal are random there should be an equal number of movements in the positive direction as in the negative, when one considers only the first movements occurring after stimulation. Holmes counted a number of first movements and found them about as equally divided between the positive and negative side as could perhaps be expected (23 : 27). Parker and Arkin found an excess of negative movements over positive of 26 per cent. Miss Smith (on the same basis of reckoning) found an excess of 39 per cent, and Adams, using different inten- sities of light, found that the excess was greater with an increase in the intensity. If the observers did not count only the first movements after stimulation but also many subsequent move- ments, the excess of negative movements is not against the sup- position of their random character. It may be well for clearness to suppose a case. Of one hundred first movements after stimu- lation (when the worms are placed at right angles to the light) there should be an equal number of positive and negative, if they are purely random. But according to the theory, negative move- ments tend to be continued while the positive ones are checked and may be followed by negative movements. This would give rise to an excess of negative movements in any large number that were counted. Holmes says that the excess of negative move- ments may be due to one of three causes — accident, failure to. count many of the slight positive movements which are easily overlooked, or to a slight orienting tendency of the light. Holmes undoubtedly has in mind first movements only, when he assumes that an excess of negative movements is against the supposition of their random character.
22 E. H. HARPER.
Holmes's theory of the "selection of random movements as a factor in phototaxis " is thus based upon observational evidence which is easy to verify. It is" easy to observe that the move- ments toward the light are apt to be checked and the movements away to be more prolonged. It is less easy to note in weak light, as the final result of orientation takes longer in that case.
ABSENCE OF RANDOM MOVEMENTS IN NEGATIVE PHOTOTAXIS
IN VERY STRONG LIGHT.
All of the experimenters referred to used artificial light except Miss Smith, who used diffuse daylight. Since all of them but Holmes took for granted the direct orienting power of light, they did not care to put the matter to a crucial test. It would seem that a test of the orienting power of light would require the use of lights of various strength, and especially of very strong inten- sity, since the perceptive power for light is so poorly developed in the earthworm. A test of the orienting power of direct sun- light is a very easy thing to make. Place the earthworm upon a sheet of wet paper in a beam of direct sunlight from a window. The light may be passed through a water chamber. The results are sufficiently obvious as to leave no doubt of their general nature. Pericliceta is oriented directly away from the light, when placed at right angles to the rays. The first effect is a turning of the anterior end away from the light and by a series of turns the worm gets into the oriented position and crawls directly away. Usually the result is produced without a false move- ment. It is immaterial whether heat effects are excluded by passing the light through water or not. A species of Lmnbricus was experimented with and behaved in the same manner.
If the sheet of paper is turned as the worm turns, so as to keep it at right angles to the rays the worm will travel in a circle con- tinuously. To show the difference between the orienting effect of sunlight and that of an ordinary artificial light the following experiment was tried. By using a sort of searchlight consisting of a tube of asbestos paper surrounding a 32 c.p. incandescent light and narrowed to a small aperture, the light was so manipu- lated by the hands as to keep it constantly directed upon the anterior end of the worm, with the worm at right angles to the
REACTIONS TO LIGHT IN THE EARTHWORM. 23
rays. In this way the worm was kept under constant stimulation and caused to turn through one complete revolution and the time required was noted. The process of turning was slow and was effected by a series of readjustments involving many trial movements in the opposite direction. Most commonly about two minutes was necessary. In twenty such cases the average time required was five minutes, the greatest time, twenty minutes.
In the beam of sunlight as before stated the worm turns con- tinuously without trial movements. The difference in behavior in the two cases is so striking that the occurrence of an occa- sional positive random movement in the sunlight is plainly seen not to affect the general result. When the worm is exposed to the sunlight, if a passing cloud obscures the sun, random move- ments begin to appear. Miss Smith, who used diffuse daylight from a north window, observed that the worm moves in a general direction away from the light, but in an uncertain manner. Adams, using a graded series of artificial lights, showed that the per cent, of negative movements increased with the intensity. Adams did not observe the whole process of orientation since he placed the worms in an illuminated box and observed the direc- tion of their movement after an interval of stimulation. Holmes used artificial light of only one strength. A Welsbach burner was also used to give an intermediate intensity between those before mentioned. Worms were used that had been kept in the dark and they were brought suddenly into this powerful light. They all moved away from the light with very little appearance of random movements. At each forward extension they would turn a little away from the light so that their path appeared like a curve. It is not meant to be stated that there were no random movements. But there could be no hesitation in saying that there was a decided difference in their reaction under the stronger light. Fresh worms would by a series of turns get into the ori- ented position frequently without a noticeable random movement. If the worms were kept in the light for some minutes, they lost sensitiveness and their random movements began to be evident.
24 E. H. HARPER.
OCCURRENCE OF POSITIVE PHOTOTROPISM.
When using a 3 2-candle-power incandescent light it was noticed that some individuals behaved positively. About 6 per cent, of 200 worms tested showed the positive reaction. But at a few inches distance from the light these worms would apparently become negative. Heat effects were not excluded however. The following is a typical instance. An earthworm crawling on a table moved straight toward a 3 2-candle-power incandescent light until within a few inches, when it began to swerve and without pausing moved in a continuous curve away from the light until it was in the line of the rays, when it continued to move in a straight line away from the light.
DIFFERENCE IN THE SENSIBILITY OF EARTHWORMS TO LIGHT IN THE CONTRACTED AND EXPANDED STATE AND THE BEARING OF THIS FACT UPON THE PRODUC- TION OF RANDOM MOVEMENTS.
The conclusion reached is that earthworms are oriented directly by light, but owing to their low degree of sensitiveness their movements are uncertain except in very strong light. The influence of light produces a number of noticeable effects upon the behavior. First, there is a state of general stimulation or restlessness inducing locomotion. Second, in light not strong enough to produce direct orientation the worm projects its anterior end in any direction. If toward the light, the worm after stretching out its anterior end will again retract it as if stimulated. If the worm is checked only after making an extension move- ment toward the light, the conclusion would seem to be that the anterior end is more sensitive when extended than when in the contracted condition. One may test this conclusion by further experiment. If a light is flashed suddenly upon a contracted worm the influence of the stimulus seems to affect it gradually, leading after an interval to movements. The extended anterior end responds far more quickly to sudden changes of stimulation. The basis for this difference in reaction must be in the fact that when the head is extended the sensitive elements in the skin are spread out over more surface than in the contracted state. A simple experiment will illustrate this fact. If an earthworm is
REACTIONS TO LIGHT IN THE EARTHWORM. 25
crawling on a moist paper it may be shaded by the hand or otherwise. When the worm crawls to the edge of the shadow and thrusts out its anterior end into the light it is jerked back suddenly. But if the light be thrown upon the worm when con- tracted, there is no sudden response, but only a gradual awaken- ing to stimulation, as evidenced by subsequent movements. The bearing of this observation upon the movements of the worm would seem to be as follows : The worm contracted is like an animal with its eyes partly closed. It extends its head at random, thus grad- ually receiving the full stimulation upon its surface. If the movement is toward the light, this causes it to contract more or less and so check stimulation. If the movement is away from the light, the oblique illumination produces less stimulation and the movement is more prolonged. An animal with eyes, as a crusta- cean, or an insect, is of course so organized that movements toward the light may be checked, as it were, at the outset, in the case of negatively phototactic animals.
It is to be observed that the earthworm begins these random movements while in the contracted state. After extension it draws up its body by means of the longitudinal muscles and is therefore in the contracted state. It then advances again, and at each advance there may be a random change in direction. Thus the worm begins these random movements when in the con- tracted state and under minimum stimulation. The nature of its locomotion and of the sensitive elements in its skin necessitates the alternation of states of low and high sensitiveness. The random movements of an earthworm under light stimulation are consequently of an entirely special character, due to causes in- herent in its structure.
To recapitulate, three situations in regard to light have been described, with their characteristic reactions. First, in weak light, second in strong light and third in a situation involving change of light intensity.
The stimulus of a change in intensity causes the animal to draw back its anterior end slightly and it then usually alters its course. When crawling under the influence of sufficiently strong light, it bends its head away from the light at each successive advance, until it gets into the oriented position. In light not
26 E. H. HARPER.
strong enough to have the directive effect its extension movements are random, an advance toward the light being checked and orientation being brought about by following up of favorable random movements. There are only two responses in reality, the checking or drawing back of the head involving the symmetrical use of the longitudinal muscles of both sides, and the turning response, involving the longitudinal muscles of only one side, that opposite to the source of stimulation. The two responses may also be combined.
THE ANATOMICAL BASIS FOR THE DIFFERENCE IN SENSITIVE- NESS TO LIGHT IN THE EXTENDED AND IN THE CONTRACTED STATE.
The text figures introduced are intended to make clear the reason for the difference in the sensibility to light of the anterior end in the contracted and extended state. Hesse, who has worked on the organs of light perception of the lower animals, has shown the structure of the light cells in many species of earthworms and has worked out their distribution segmentally. He shows that these cells are most numerous on the first seg- ment, and especially on the prostomium (which is fused with the first segment in Perich&td) and that their number diminishes rapidly on each segment as we go farther back. It is conse- quently the very tip of the animal ( the posterior tip as well ) which is most important for the perception of light, although light cells are found in small numbers over the whole length of the body.
The sections of PcricJiceta (Figs. I and 2) show that the first segments are subject to great extension and contraction. It was not possible to get the worm fixed in the fullest state of either extension or contraction. In Fig. 2 it is seen that the first seg- ment is partly inrolled into the buccal cavity in the state of con- traction. For further demonstration of this point the epithelial layer alone, of the first segment, is represented in the extended and the contracted state in Figs. 3 and 4. It is seen to be greatly thickened as well as inrolled when contracted. The effect of this on the light cells is seen by comparison of Figs. 5 and 6. The light cells are on the basement membrane. The thickening
REACTIONS TO LIGHT IN THE EARTHWORM.
The figures illustrate certain features of the worm in the extended and in the con- tracted state. The states of extension and contraction represented are not the most complete possible.
FIGS. I and 2 are sagittal sections of the first five segments of an extended and a contracted worm respectively. (<?) body wall, (£) everted buccal cavity slightly protruding, which is used as a proboscis. It is to be noted that the first segment, which is the most sensitive to light, is partly inrolled in Fig. 2
FIGS. 3 and 4 are sections of the dorsal epithelium of the first segment of an ex- tended and contracted worm respectively in the same plane as the last.
FIGS. 5 and 6 give sections of epithelium in the extended and contracted condi- tion. (/. f.) light cell.
28 . E. H. HARPER.
of the epithelial layer must of course tend to cut off light from these cells. The inrolling of the most sensitive region is another important factor.
THE BEARING OF EXPERIMENTAL RESULTS UPON THE HABITS
OF THE EARTHWORM.
It is a truism that in all experiments upon animals the relation of the experimental results to the normal life of the animal should be kept in mind. The behavior of the earthworm has not been systematically studied as a whole except by Darwin. It is obvious that all the experimenters mentioned have studied the reactions of the earthworm in only one phase of its activity, and that phase is not what we should call the normal life of the worm. It is as if the experimenters had chosen the situation of the earth- worm as we find it crawling on the sidewalks after a heavy rain as being its typical mode of life. None would probably admit this sooner than themselves, and doubtless they have regarded certain facts as too obvious to require mention. Does the fact that the normal life of the earthworm is carried on in a burrow affect our view of the experimental results obtained ? Now the earthworm does spend a portion of its life, during the night time, crawling on the surface of the ground in search of leaves, and also during sexual activity it is less mindful of the light, as is stated. The earthworm leaves its burrow rather reluctantly. Darwin describes the earthworm as retaining the posterior end in the burrow while making searching movements in all directions in search of leaves. In drier weather we know that worms burrow deeply and seldom are found near the surface, depositing their castings in old burrows instead of on the surface.
If the worm is at home almost exclusively in the burrow we should expect those responses which are typical of the burrow life to be better organized and more definite than its activities when crawling in the open. The movements which are typical of the life in a burrow are mainly in the line of the axis of its body. Are these movements and the responses which control them of a more definite nature than its lateral movements ? We may first consider the typical burrow movements in response to light. These may be imitated easily by using a screen to shade
REACTIONS TO LIGHT IN THE EARTHWORM. 29
the worm or portions of it while crawling on a moist surface, preferably covered with a thin layer of dirt.
If a worm which has been kept in the dark is placed on the moist surface, and the screen is suddenly moved so as to expose the anterior end to light, it contracts the anterior segments slightly, sometimes so slightly as to be barely noticeable, and crawls back- ward into the shadow. If the posterior end be illuminated in the same way the worm crawls forward into the shade, but after a noticeably longer interval. A slight twitching of the posterior end may be noticed at first, if the light is suddenly turned on. The worm always crawls forward when stimulated posteriorly, If a worm is crawling backward it can always be reversed by stimulating the posterior end. Crawling backward is of course the method by which the worm comes to the surface to eject castings. The two sorts of responses described are of the kind called " photopathic " as distinct from phototactic, and they serve of course to inhibit the worm from leaving its burrow in the light. These " photopathic " responses are very definite and the stimulus calling them forth may be quite weak light. Adams has shown that in very weak light AllolobopJwra fcetida is positive and he suggests that the worm leaves its burrow in response to the stimulus of very weak light upon its anterior end. These ob- servations show that the movements of the worm in its burrow are very definitely controlled by the light, so far as they may come in contact with it by their more"sensitive anterior and pos- terior ends. The middle of the worm is less sensitive to light but its sensitiveness may be shown in the following way.
If the worm is placed on the moist surface exposed to full light from overhead (a 32-candle-power incandescent was used, at a distance of 15 inches) and a screen is then brought over the posterior part of the body leaving the anterior end exposed, the worm does not draw back as when the anterior end was suddenly illuminated. Instead it begins to make random movements in various directions. It may crawl farther out into the light, thus bringing the middle portion into stimulation. This movement is however checked before the more sensitive posterior end is ex- posed. After a noticeable latent period showing the lower sensi- tiveness of the middle portion, the worm crawls back under the
3O E. H. HARPER.
shade rather quickly, but usually not completely. The com- monest way in which the worm gets under the shade is as fol- lows : It makes all sorts of random movements in every direction, and tries to burrow into the thin layer of dirt, until it acci- dentally gets the tip of the anterior end under the shadow of the screen. It then at once is oriented, so to speak, and crawls com- pletely under the glass. It may crawl under as if circling around a post. The imaginary post may be exposed to the light so that the posterior part has to crawl forward into the light to get around the post. Usually, however, the anterior end travels faster so as to jerk the middle part under the screen at once.
These so-called " photopathic >: reactions are consequently very definite and predictable because they are adaptations im- portant in the normal life of the worm. As compared with the random lateral movements we see that they are controlled by weaker stimuli and are more definite. The anterior and posterior ends are more sensitive than the middle for the obvious reason that the ends alone come into contact to any great extent with light stimulation.
The lateral movements, which are typical of life outside the burrow, are as we have seen of a random nature and less defi- nitely controlled. The worm " dashes back like a rabbit into its burrow," to use Darwin's expression, under a weak stimulus. But when crawling on the surface the same strength of stimulus produces only a general irritation and swaying random move- ments occur which lead to orientation away from the light only after many trials. With a higher intensity of light the worm is oriented more quickly. Thus we see that a very high stimulus is required to produce a direct sidewise movement away from the light while a very weak stimulus will cause it to move back into its burrow away from the light. The random lateral movements are aptly described by Holmes as " inconsequential vermicula- tions." But this description does not apply to the movements which are typical of its burrow life. The worm is as definitely adapted to the burrow and as little adapted for life in the open as some other burrowing animals of higher rank that could be mentioned. However this statement must be modified when we consider that a worm exposed to the light on the ground does not
REACTIONS TO LIGHT IN THE EARTHWORM. 3!
trouble to make random movements but begins to burrow into the soil immediately. After heavy rains we see them washed out of their burrows, and crawling in unwonted places when they are unable to burrow.
REACTIONS TO MECHANICAL STIMULI.
Pcric/ueta goes through its peculiar jumping movements only under mechanical or similar stimulation, never under the influence of light, so far as we have observed. When touched with a needle on the anterior end it contracts the anterior segments slightly and may begin to crawl backward or it may go forward, lifting its head and making various random movements before settling on any direction. With a slightly stronger stimulus the anterior end turns away slightly from the stimulus. Increase the stimulus and the worm may contract the longitudinal muscles of the opposite side so as to jerk the body around 90 or even 180 degrees, and so give it a new direction. Or the worm may go off into a whole series of jerks, so that there is a complete grada- tion between the extent of the responses, depending upon the stimulus. More important as determining the extent of the reaction is the condition of the worm. Well-fed worms in fresh condition, when just dug out of their burrow, spring around in the liveliest fashion. If handled they give a series of movements which must make it difficult for an enemy, a bird, for instance, to pick them up before they get a chance to crawl under cover. When stimulated they exude an abundant yellowish mucus. Whether this is an offensive secretion to its enemies is not known to the writer. When a point in the middle of the worm is stimu- lated the body recoils away from the stimulus at that point and there is a slight swelling due to contraction of the longitudinal muscles, like the contraction and shortening of the anterior end under stimulation. Occasionally the worm may move violently toward the stimulus, but this seemed to be due to an overstimu- lation producing a complex of effects rather than a simple reflex.
The leaping movements of Pericli<zta are certainly the best examples of random movements that are afforded. They are exclusively adapted to those chance circumstances when the worm gets out of its burrow. They lead in no definite direction,
32 E. H. HARPER.
though they may carry the worm to a considerable distance and enable it to distract the enemy. They are a conspicuous example of the character of most movements of the earthworm, which belong to its limited life outside the burrow.
CONCLUSIONS.
The method of reaction to light of the earthworm is far removed from the sort of "trial and error method" of the Infu- soria, as analyzed by Jennings. Its avoiding reaction in strong light is of the nature of a definite reflex which causes it to turn directly away from the stimulus, if the whole body is in the light, or to retreat into its burrow, if only the anterior end is stimu- lated, or go forward if the posterior end alone is stimulated. Methods of trial and error in reaction to light and other ordinary stimuli have clearly been supplanted by more definite responses in all but the Protozoa and certain other low types of animal life. The earthworm's reactions to stimuli, mechanical, thermal, chemical, are in general such as its nervous system and muscu- lature would lead us to expect. The occurrence of random movements in response to all but very strong light is the out- come of the undeveloped condition of its organs of light per- ception, not to the want of a nervous system and musculature adapted for such simple reflexes. Diffuse organs of light per- ception may not respond definitely to a localized stimulus unless it is a very strong one. The trial and error method of its responses to relatively weak light are exceptional in character in com- parison with its reactions to other ordinary stimuli. Its archaic type of end organs for light gives rise to a type of behavior which is to be regarded as primitive. For the trial and error method is clearly supplanted in the ascending scale of animal life, by reactions of a definite nature, in the case of the simple responses to the ordinary stimuli.
SUMMARY OF RESULTS.
1. PcricliiCta bcrmudensis (Beddard) is an exotic earthworm found sometimes in greenhouses. Its active habits are one of its chief characteristics.
2. The body is less sensitive to light when contracted than
REACTIONS TO LIGHT IN THE EARTHWORM. 33
when extended, owing to the fact that when extended the sensi- tive elements are spread out over a greater surface and become more susceptible.
3. In locomotion, as there are alternate extensions and con- tractions, there is an alternation of the condition of lower and of higher sensibility. This is important particularly in the sensitive anterior end.
4. As the worm begins each extension in a condition of lower sensibility, it may project its anterior end toward the source of light. This movement is checked as soon as the increased sensibility of the extended anterior end appreciates the stimulus. Movements away from the light do not meet such a check and so are prolonged farther. Orientation is the result of a trial and error method.
5. In strong enough light, random movements toward the light are suppressed altogether, and the worm appears to move djrectly away from the light without noticeable trial movements. This applies to worms which have been kept in the dark and are in a perfectly fresh condition, as after a time they lose their dis- crimination and begin to make random movements.
6. Movements in the longitudinal direction are typical of the normal burrow life of the animal, and the axial movements initiated by the anterior and posterior ends are more definitely controlled by the stimulation of light and by a weaker stimulus than are the lateral movements. Lateral movements tend more to be random and are directed only by stronger stimuli because the organization of the worm is chiefly in adaptation to a burrow- ing life and not to an open air life.
7. The characteristic leaping motion of Perichcefa is a con- spicuous example of random lateral movements, adapted to life outside of the burrow. All gradations may be observed between the ordinary reaction to a slight local stimulus by jerking back, and also bending the body away, if the stimulus be stronger, up to a complete series of leaping movements.
8. Reactions to mechanical stimuli, as well as to other stimuli, chemical, thermal and electric, show that the worm is like other animals as highly organized as itself in responding to a local stimulus of an injurious nature by contracting and bending away
34 E. H. HARPER.
in a definite " avoiding reaction." In this respect the effect is like the response to very strong light. Consequently we see that the random reactions to weaker light have a special explanation and are only an apparent exception to the general form of nega- tive response.
BIBLIOGRAPHY. Adams, George P.
'03 On the Negative and Positive Phototropism of the Earthworm Allolobophora foetida (Sav. ) as Determined by Light of Different Intensities. Am. jour. Physiol., Vol. IX., No I.
Gar man, H.
Bulletin of Illinois State Lab. of Nat. Hist., Vol. III., Art. IV. Note p. 74.
Hesse, R.
'96 Untersuchungen iiber die Organe der Licht-Empfindung bei niederen Thieren. Zeit. wiss. Zool., 6l, p. 393.
Holmes, S. J.
'05 The Selection of Random Movements as a Factor in Phototaxis. Journ. Compar. Neurology and Psychology, Vol. XV., No. 2, pp. 98-112.
Jennings, Herbert S.
'04 Contributions to the Study of the Behavior of Lower Organisms. Published by the Carnegie Institution of Washington.
Parker, G. H. and Arkin, L.
'01 The Directive Influence of Light on the Earthworm Allolobophora foelida (Sav.). Amer. Journ. Physiol., IV., pp. 151-157.
Smith, Amelia C.
'02. The Influence of Temperature, Odors, Light, and Contact on the Move- ments of the Earthworm. Amer. Journ. Physiol., VI., pp. 459-486. ZOOLOGICAL LABORATORY,
NORTHWESTERN UNIVERSITY,
EVANSTON, ILLINOIS, August 14, 1905.
SOME POINTS REGARDING THE BEHAVIOR OF METRIDIUM.
LULU F. ALLABACH.
It has recently been shown that the reactions of many sea anemones are modifiable, in dependence on a variety of internal conditions (Jennings, 1905). The purpose of the work here pre- sented was to determine how far similar relations hold for Mctri- dinni niarginatinn. Since jMctridimn is the commonest of our sea anemones, and the one most used in investigation and in- struction, it is important that its behavior should be well known. The work was suggested by Dr. H. S. Jennings, and carried out under his direction at the Marine Biological Laboratory at Woods Hole.
I. CHANGES IN THE REACTIONS TO CERTAIN SORTS OF
FOOD BODIES.
The point to which experimentation was first directed was the interpretation of the results of certain experiments of Nagel (1892) and Parker (1896). In Parker's experiments alternate pieces of meat and filter paper (soaked in meat juice) were given to the tentacles of one side of the disk of Mctridiuin. It was found that while the meat was swallowed each time with equal readiness, the time taken in swallowing the paper increased, and after three or four trials the animal no longer ingested the paper, though the latter contained each time the same amount of meat
o
juice as at first. After reaching this result with the right side of the disk, the same series of experiments was performed on the opposite side of the disk of the same specimen. It was found that the left side* had not become modified by the experience of the right side. It at first took the paper, then by the same gradual change seen previously on the right side, it came to refuse the paper. A series of records of the times required for swallowing the meat and paper in such an experiment by Parker are given in the following table :
35
LULU F. ALLABACH.
|
Right Side. |
Left Side. |
Right Side. |
Left Side. ' |
||
|
I. Meat |
85 sec. |
45 sec. |
9. Meat |
70 " |
35 sec. |
|
2. Paper |
80 |
90 |
10. Paper |
— |
85 « |
|
3. Meat |
5° |
45 |
II. Meat |
40 " |
30 " |
|
4. Paper |
90 |
— |
1 2. Paper |
95 " |
|
|
5. Meat |
40 |
45 |
13. Meat |
35 " |
|
|
6. Paper |
I°5 |
55 |
14. Paper |
— |
|
|
7. Meat |
5° |
35 |
15. Meat |
35 " |
|
|
8. Paper |
105 |
16. Paper |
— |
What is the cause of the change of behavior in these experi- ments ? Several possibilities suggest themselves :
1. Jennings (1905) found that in Aiptasia similar effects were produced, and in this case the result was evidently due mainly to changes in the state of hunger. The very hungry Aiptasia took meat and paper readily, but after feeding a -short time it refused paper, and later it came to refuse meat also. The animal could be caused to refuse paper more readily by feeding it meat alone than by feeding paper alone or by feeding the two in alternation. It was evident that the changed reaction toward paper was due to loss of hunger. We must inquire whether this factor plays a part in Metridium.
2. Nagel (1892) referred the changes in reaction toward paper to a process corresponding to what we call judgment in higher animals ; he held that the animal discovers by experience that the paper is unfit for food, and thereafter refuses to take it. Such a process in so low an animal would of course be of great interest, and the evidence for it needs to be examined carefully. Nagel held that it was owing to the lack of close nervous inter- relation of parts in these animals that the experience of one side is not transmitted to the opposite side.
3. Parker sums up the phenomena shown in these experiments as follows : " The successive application of a very weak stimulus is accompanied, not by the summation of the effects of stimula- tion, but by a gradual decline in these effects, till finally the response fails entirely" (Parker, 1896, p. 116).
In my experiments I attempted to test these different possi- bilities, and to work out in a systematic way the various factors which modify reactions in Metridimn.
The taking of food has been well described by Parker (1896). It is important to note that ciliary action plays a large part in the
BEHAVIOR OF METRIDIUM. 37
taking of food by Mctriduim. Muscular movements of the ten- tacles, disk, and oesophagus also plays a part, but a less impor- tant one than in the anemones studied by Jennings (1905). The tentacles bearing bits of food are bent toward the mouth, and the cilia of the tentacular surface carry the food toward the mouth opening. The cilia of the oesophagus are usually beating out- ward, but when food enters the mouth the stroke of the cilia of the part in contact with the food becomes reversed, so that the food body is conveyed inward (see Parker, 1896, 1905). I have found that the reversal of the cesophageal cilia is frequently caused in JMctridiuui by indifferent solids, such as filter paper, so that such bodies are ingested.1 There is much variation in regard to this matter, some individuals take filter paper readily, others slowly and only at times, others not at all. As we shall see later, this depends largely on the degree of hunger.
We will now take up experimentally the various possibilities of modification above distinguished. In studying these matters, it is most important that specimens which are fresh and in good condition should be used, otherwise clear results will not be
7
obtained.
I. Hunger. — Conditions of hunger and satiety affect the food reactions of Metridinin in a most decided way. When the animal is very hungry (and in good condition otherwise), the column is extended, becoming long and slender, while the disk is widely spread, and the tentacles extend a considerable distance beyond its edge. If the animal remains contracted, it can often be in- duced to extend by placing a piece of clam meat or some meat juice on the infolded disk. Two or three applications of food will often cause the most obstinately contracted specimens to ex- pand beautifully. If now a piece of mussel of considerable size (having an area equal to the cross section of the column, with a thickness of three or four millimeters) is brought near the edge of the disk, so as to come in contact with the tips of two or three tentacles, a decided reaction is produced. The tentacle tips ad- here to the meat, and the tentacles and adjacent parts of the disk contract quickly, so that the piece of meat is drawn inward. It
1 This was possibly due, as Parker (1905, 1905*7 } has set forth, to the paper's having been touched by the fingers ; this matter was not tested.
38 LULU F. ALLABACH.
thus comes in contact with many other tentacles, these bend down upon it. Then all bend over toward the mouth, while at the same time this portion of the disk contracts. Thus the food is brought nearer the center of the disk. The mouth meanwhile opens, and the food is passed into it, partly by the ciliary action of the tentacles, partly by muscular contractions of tentacles, disk and mouth. The latter factors play a more important part in the reaction of a hungry specimen to a large piece of food than does ciliary action.
After ten or a dozen good-sized pieces of meat have been swallowed, the reaction becomes much slower. If the meat is brought in contact only with the outer tentacles, these no longer react, and such food is not taken. If placed on the inner ten- tacles, the meat is slowly transferred to the mouth, where it is swallowed. The animal is frequently in this condition when brought into the laboratory ; food placed on the outer tentacles is refused, while that on the inner tentacles is taken.
The reaction of the tentacles becomes slower as more food is taken, so that the process of ingestion takes a much longer time than at first. Finally, all the tentacles cease reacting to food, and it is not carried to the mouth. But if the meat is placed by the experimenter directly on the mouth, it is ingested. This ap- pears to take place almost alone through the action of the cilia ; the reversal of the cilia seems to be more nearly independent of the physiological states of the animal than are the contractions of the muscles. The mouth never reaches a condition where it rejects pieces of mussel placed directly upon it. So much food may be taken that the body becomes puffed out to form a swol- len sack, yet new pieces are forced inward. Large pieces of meat may however be refused even when placed directly on the mouth, the lack of assistance from muscular contractions appearing to make it impossible for the cilia to draw them inward. The feed- ing may be carried so far as to cause internal disturbance, result- ing in the disgorgement of the food. But immediately after such disgorgement the mouth will take new food. Sometimes when the animal is nearly filled, a large piece of meat placed on the mouth is partly swallowed, then partly disgorged by a convulsive movement, then the swallowing is resumed. This may happen repeatedly.
BEHAVIOR OF METRIDIUM. 39
The loss of reaction on the part of the tentacles after much food has been taken is not due to fatigue resulting from their activity in taking food. This is demonstrated by the following facts : (i) The animal may be fed from one side of the disk till it is satiated. Now meat given to the opposite side of the disk is not taken, though the tentacles of this side have not been active, and so cannot have become fatigued. (2) Seven hours after the animal has been fed all it will take, the tentacles still refuse to take food, though they have had this period for recuper- ation. Actual fatigue, as we shall see later, lasts but a few minutes.
The effects of hunger and satiety are further seen in the reac- tions of Mctridinin to indifferent bodies, such as bits of filter paper. These are commonly taken readily by hungry specimens of Mctridinui. The tentacles react to them, just as to meat, so that they are carried to the mouth. Here they cause the reversal of the ciliary movement in the same way as does meat, so that they are carried inward. But after the animal has been fed a considerable quantity of meat, it will no longer take filter paper. First the outer tentacles refuse it, later the inner ten- tacles, and finally the mouth. A piece of filter paper placed squarely on the mouth no longer causes the reversal of the stroke of the cilia of the oesophagus, so that it is not carried inward.
The fact that the reversal of the cilia under such stimuli depends on the physiological state of the animal is one of much interest. It shows that the cilia are not entirely independent of such states, as some other facts would seem to indicate.
Seven hours after the animals had been fed an abundant meal of mussel meat, they still refused to take filter paper, though before the meal paper was taken readily.
Thus it is clear that the state of the processes of metabolism is in j\lctridinin, as in other sea anemones, a most important factor in determining behavior under mechanical and chemical stimuli. But it is equally clear that this will not explain the results of Parker's experiments, described in the first paragraphs of this paper. Parker found that after one side of the disk has refused to take paper, the other side still accepts it. In repeating
4O LULU F. ALLABACH.
Parker's experiments, I fed in one case six successive regions of the disk, each till it had rejected food ; the next would then take it as readily as at first. This refusal then cannot be due to a general lack of hunger, and we must examine the other explana- tions that have been given.
2. "Judgment." — If the animal comes to reject paper through experience of the fact that the paper is not good for food, there must be some way in which this experience is obtained. It might be supposed that this comes through swallowing the food ; being indigestible, its effect after swallowing might cause the animal thereafter to reject it. This was tested by preventing the swallowing of the paper. The animal was fed meat and paper in alternation, as in Parker's experiments. But after the paper had been carried to the mouth and was passing down in the oesophagus, it was removed with a fine pair of tweezers. This is easily done without disturbing the animal. Thus the bits of paper never reach the digestive cavity. Yet the animal comes to reject them as quickly as before. After a few alternations of meat and paper, only the meat being completely swallowed, the animal ceased to take the paper, while it still accepted the meat. Hence the effect of the paper after it reaches the digestive cavity is not the cause of its rejection.
Furthermore, nothing like a contrast or comparison between the meat and the filter paper is necessary in order to induce the rejection of the paper. If successive pieces of paper were fed alone to the anemones, they soon came to reject these as before. In such cases it is noticeable that the animal takes a larger num- ber of pieces of paper than when the paper is fed in alternation with meat. The number of pieces required is about the same as the number of pieces of meat and paper together that result in rejection of the paper when the two are given in alternation. This fact throws some light on the cause of the rejection, as we shall see later.
3. Repetition of Weak Stimuli, till Effect Fails. — Is the loss of the positive reaction to the paper due to the general fact that weak stimuli, when repeated, gradually lose their effect ? This was tested by excluding this factor from the experiments, in the following way. A given specimen was first tested and found to
BEHAVIOR OF METR1DIUM. 4!
accept filter paper (in some cases plain, in others soaked in meat juice). After this first test, the same region of the disk was fed successive pieces of meat, which were all readily taken. After eight to twelve pieces of meat had been accepted, a piece of filter paper like that originally accepted was given to the same region of the disk. // tvas not accepted. This experiment was repeated with many specimens, always with the same result. This result was likewise reached if the animal was not allowed to complete the swallowing of the meat, the latter being removed after it had passed into the oesophagus. This, of course, shows conclusively that loss of hunger is not the cause of the change of reaction toward the paper.
The placing of meat juice on a certain region of the disk causes the food reaction, as Parker has shown. If this experi- ment is tried successively a dozen times in the same region of the disk, the animal comes to reject filter paper in this region, as in the experiments described in the foregoing paragraph.
Thus it is not necessary that weak stimuli should be repeated in order that the animal shall reach a state in which it fails to react to them. Repetition of strong stimuli (meat) causes failure to react to weak stimuli just as readily as does repetition of the latter. Repetition of strong stimuli alone, of weak stimuli alone, and of the two in alternation, all have the same effect ; the animal ceases to react to weak stimuli.
In all cases in which meat is fed to a given region, moreover, the reaction to strong stimuli ceases some time later than that to weak stimuli. After giving a certain region sixteen to twenty pieces of meat, meat is no longer accepted here, though other regions of the disk take it readily.
4. Fatigue. — The facts brought out in the foregoing para- graphs seem to make possible a clear interpretation of the rejec- tion of the paper. It is evidently a case of plain fatigue. After stimulating a certain region of the disk a number of times, it ceases to react — first to weak stimuli, then to strong stimuli - though other parts react as before. The same results are pro- duced whether the successive stimuli are all strong or all weak, or partly strong and partly weak. It appears evident therefore that it is the reaction of the animal, not the precise character of
42 LULU F. ALLABACH.
the stimulus, that causes the fatigue. This is perhaps what should be expected when the nature of the food reactions is taken into consideration. In taking food the region in contact with the food produces a very large quantity of mucus, envelop- ing the food body. It is not surprising that successive imme- diate repetitions of this excessive production of mucus gradually exhausts the region. As is usual in fatigue, strong stimuli may produce reaction for some time after weak ones have failed.
The fatigue thus caused usually lasts only two to five minutes. After this period has elapsed the fatigued region is frequently as ready to take food as before - - provided the animal is still hungry.
Nagel and Parker have held that the result of their experi- ments " illustrates the extreme looseness, or even independence, of the nervous activities of the two sides of the animal " (Par- ker, 1896, p. 1 1 6) --since the effects of the experience of one side are not transmitted to the other side. With the recognition that these results are a simple matter of fatigue, they perhaps cease to have any bearing on the question of the closeness or looseness of nervous interconnection. In the highest organisms, as man, fatigue induced by repeated contractions of a finger of the left hand, in erogographic experiments, is not transmitted ap- preciably to the right hand. But the experience gained by touch- ing a hot iron with the left hand would nevertheless later prevent the right hand from touching it.
II. OTHER MODIFICATIONS IN BEHAVIOR.
A very peculiar modification of behavior is seen in the follow- ing : A specimen refuses to take filter paper, though it still takes meat. After it has thus refused paper, two or three pieces of meat are given in succession, and taken readily. Now the bit of paper is again placed on the disk, and it too is swallowed. Clearly, the uninterrupted taking of a number of pieces of meat changes the physiological condition of the animal in some way, preparing it for the taking of any object with which it comes in contact. (After a larger number of pieces of meat, the paper is refused, as we have before seen.)
Acclimatization to weak stimuli is readily demonstrated in fresh, active specimens of Metridium. If a light stream of water
BEHAVIOR OF METRIDIUM. 43
is directed with a pipette against the expanded disk, the animal contracts strongly. Waiting till it has again expanded, the stream of water is directed upon it as before. This time it does not react. In specimens that are not in good condition, this change of behavior cannot be seen. The animal does not con- tract at all save under strong stimuli, and if such are repeated, it contracts as at first.
PAPERS CITED. Jennings, H. S.
'05 Modiriability in Behavior. I. Behavior of Sea Anemones. Journ. Exper. Zool., II., No. 4.
Nagel, W. A.
'92 Das Geschmacksinn der Actinien. Zool. Anz., XV., 334-338. Parker, G. H.
'96 The Reactions of Metridium to Food and Other Substances. Bui. Mus. Comp. Zool. Harvard College, XXIX., 102-119.
'05 The Reversal of Ciliary Movements in Metazoans. Amer. Journ. Physiol., XIII., 1-16.
The Reversal of the Effective Stroke of the Labial Cilia of Sea Anemones by Organic Substances. Amer. Journ. Physiol., XIV., 1-5.
THE INFLUENCE OF THE NERVE ON THE RE- GENERATION OF THE LEG OF DIEMYCTYLUS.
CECIL SHEPARD HINES.
The following experiments were carried on at the suggestion of Professor Morgan, for the purpose of ascertaining whether regeneration in the leg of Dicinyctyhts is dependent on its con- nection with the nervous system, as has been found in the case of other urodeles, or whether the supposed result may not have been due to unintentional injury to the blood supply. The hind limb was chosen for operating on account of its larger size. The general course of procedure was to cut the nerve in the upper part of the leg without injury to the artery, and then amputate the leg at the knee joint. After a period of a little more than three weeks the new part can be clearly recognized as a dark protu- berance sharply contrasting with the lighter color of the sur- rounding skin.
In the first lots the nerve was cut as near the proximal end of the femur as possible. A longitudinal slit through the skin was made with a sharp knife. The muscles were then separated until the nerve was brought into view. Care was taken not to injure the blood vessel which closely adheres to the nerve and is almost inseparable from it. If the operation were performed without injury to the blood vessel and the leg showed a result- ing paralysis it was amputated at the knee. For comparison an equal number of salamanders had the leg cut off without injuring the nerve or blood vessel. The results obtained from the first series seemed to show that regeneration in Dicmyctylus was in no way dependent upon the nerve. The proliferation of new ma- terial began as soon in those in which the nerve had been cut as it did in the checks. Nor did the amount of material regener- ated seem to be affected in any way. There were, it is true, great variations in the rate of regeneration, but these seemed to arise from purely individual differences, and to bear no definite relation to the presence or absence of the nerve connection. In two checks operated upon on the same day and kept in the same
44
INFLUENCE OF NERVE ON REGENERATION. 45
aquarium, so that external conditions could play little, if any, part in the result, an interval of ten days or more might occur between the earliest and latest appearance of proliferation. The results obtained after cutting the nerve at this level may have been due to the presence of collateral nerve-connection sufficient to give the required stimulus to the tissue ; for as was later clearly shown, the nerve is an important factor in the regeneration.
In the succeeding series the nerve was cut through the pelvic girdle close to the backbone, in the hope of more completely cutting off the nerve supply of the limb. The incision necessarily went through into the body cavity as the nerves given off from the spinal cord lie close to the inner wall and are covered only by ccelomic epithelium. The operation is by no means as serious as would be imagined, since the wound heals completely in three days. During this time the animal acts in a perfectly normal manner except for the injured leg. Instead of using separate individuals for checks as before, both legs of the same individual were amputated, but the nerve was cut on one side only. The males are much more difficult to operate upon than the females, on account of their greater muscular development, whereas in the female the pelvic girdle stands out prominently and the body wall is thin. In the males the girdle is not visible externally and is overlaid by a thick musculature which renders operating upon the animal at this point difficult.
On November 26 a set of seven salamanders was operated upon as described above. They were not again observed until the forty-fifth day. At that time both legs of each individual had proliferated material to a greater or less extent. The side used as a check could be identified in every case but one, by its far greater amount of proliferated material.
In the exception the animal assumed a peculiar green color, evidently from a disease, and at a later period both legs were entirely sloughed off. This set was continued under observation until the eighty-third day, at which time there was still a decided difference between the appearance of the two sides, although by no means as pronounced as before. The check showed in each individual the foot plainly differentiated, while in only two in- stances was this the case upon the other side, and even in those cases to a much less extent.
46 CECIL SHEPAKD HIKES.
Later I operated upon at least thirty salamanders in several lots. Some of these were starved while others were well fed. The abundance or lack of food did not seem to be a factor in the rate of regeneration. Salamanders which were reduced almost to "skin and bones" showed the same comparative amount of regeneration as well-fed individuals. The influence of food did show itself, however, in the amount of material proliferated. During starvation an individual shrinks greatly in size and pro- liferates much less material for the same relative amount of regeneration as a well-fed companion.
To ascertain whether the blood supply was a factor in regen- eration the artery of several individuals was cut just above its entrance into the leg, the nerve being left intact. The result showed that the leg regenerated at the normal rate. However, not much stress can be laid upon this experiment, owing to the rapidity with which a sectioned blood-vessel heals.
That the circulation in the leg may have continued to some extent after the operation in those individuals whose nerve as well as artery had been sectioned near the backbone was shown conclusively by the following experiment. A salamander was taken and a cut made in the pelvic region as before. Then a vein was severed in the lower part of the leg. This continued to bleed freely for a considerable time, as would not have occurred had the total blood supply been cut off. The collateral blood supply probably still brought blood to the limb. Similarly the collateral nerve supply may in the first series of experiments have sufficed to keep the regeneration up to the same rate as in a limb in which the nerve was not cut.
In a number of cases regeneration did not set in at all on the side on which the nerve had been cut. At least, after a period of two months and a half there was not the least sign of prolifer- ation, while in the normal course of regeneration the new part appears in about twenty-five days. This lack of regeneration is probably due to the distal end of the nerve being displaced, and in consequence the regenerating nerve was unable to grow down its old path along the degenerated nerve, but was turned aside. Consequently not even a retarded regeneration occurred.
The most important work bearing on the question of the rela-
INFLUENCE OF NERVE ON REGENERATION. 47
tion between the nerve and the regeneration of the leg is that of Wolff.1 He found that if the nerve-cord were destroyed in the region of origin of the leg nerve that the leg regenerated at the normal rate. Since the spinal ganglion was left after this opera- tion, its presence may have sufficed to produce the result. In fact, nerves were found in the new foot. In order to remove the ganglion also, a piece of the spinal column was cut out including cord and ganglion. Six individuals that survived this operation showed that after the first proliferation of new material had taken place growth came to a standstill for a time and then began again. The result suggests, Wolff thinks, that the standstill was due to the lack of nerve connection, while the renewal of growth was due to the reestablishing of a new nerve connection. In fact the disabled leg showed some signs of having regained its power of motion.
Wolff discusses the question whether the period of standstill may not have been due to the lack of function or activity of the leg while its later growth was due to its regaining its loco- motor function. He argues that this is probably not the case, but that the nerve connection is directly responsible for the result.
A student of Busfurth's, R. Rubin,2 has obtained similar results. What part the nervous connection plays in these cases is still obscure. Morgan and Davis3 have found that for the regeneration of the tail of the tadpole, the presence of the noto- chord and not the nervous system is the important factor.
COLUMBIA UNIVERSITY.
1 Virchow1 s Arthiv, CLXIX., 1902.
2 Archiv Enfw. Mec/i., XVI., 1903. * Archiv Ent-w. Mech., XV., 1903.
Vol. X. January, 1906. No. 2
BIOLOGICAL BULLETIN
AN EXAMINATION OF THE METHODS FOR THE MICROCHEMICAL DETECTION OF PHOS- PHORUS COMPOUNDS OTHER THAN PHOSPHATES IN THE TISSUES OF ANIMALS AND PLANTS.
R. R. BENSLEY. (From the Hull Anatomical Laboratory, University of Chicago. )
The microchemical reaction for the detection of phosphorus in the tissues of animals and plants introduced in 1898 by Macal- lurn ('98) is a modification of that devised in 1893 by Lilienfeld and Monti ('93). These investigators attempted to demonstrate the distribution of phosphorus in tissues by subjecting the latter for some time to the action of a solution of ammonium molyb- date in nitric acid, after which they were treated with a solution of pyrogallic acid. The nitric molybdate reagent was supposed to liberate the phosphorus from its organic combinations, to convert it into orthophosphoric acid, and finally to precipitate the latter as the yellow phosphomolybdate of ammonium. The further treatment of the tissues with pyrogallic acid had for its object the reduction of the ammonium phosphomolybdate to a lower oxide of molybdenum, which, according to Lilienfeld and Monti had a brown or black color. In this way the pale yellow precipitate containing the phosphorus was converted into a dark-colored pre- cipitate which could be easily studied under the microscope.
The importance of a microchemical reaction which would ena- ble us to determine accurately the distribution of the compounds of phosphorus not only in the tissues but also in the parts of the cells of the tissues can hardly be overestimated. It is therefore
49
5O R. K. BENSLEY.
not surprising that the results of Lilienfeld and Monti have been subjected to careful experimental examination by a number of other investigators.
Raciborski ('93) in 1893, in his review of Lilienfeld and Monti's article, showed that the reaction of ammonium phosphomolybdate with pyrogallic acid resulted in the production of a green com- pound, while ammonium molybdate gave by reduction with the same reagent a brown compound. He concluded that the brown reaction of Lilienfeld and Monti was due to ammonium molyb- date mechanically imbibed by the section, and not to ammonium phosphomolybdate.
Heine ('96), also, showed that phosphorus-free histone, pre- pared from the thytnus, formed with the nitric-molybdate reagent compounds from which the ammonium molybdate could not be removed by washing in water, and in which it could be detected by the use of reducing compounds. For this purpose he em- ployed stannous chloride.
Macallum confirmed Raciborski's observations as to the color compounds produced by the reduction of ammonium phospho- molybdate and ammonium molybdate respectively, and showed that ammonium molybdate could not be removed from tissues which had been treated with the nitric-molybdate reagent even by washing for several months in changes of distilled water. Macallum perceived the necessity of substituting for pyrogallic acid, which gives colored compounds with both the phospho- molybdate and the molybdate of ammonium, some reagent which would discriminate between these two compounds, and give a color reaction with phosphomolybdate alone. This condition he found to be fulfilled by zinc chloride, previously introduced for this purpose by Polacci ('94), which gave a green color with the phosphomolybdate but did not act on ammonium molybdate. Owing, however, to the fact that zinc chloride acted very slowly, he finally adopted as a reducing agent phenylhydrazin hydro- chloride, which, according to him, made a very marked distinc- tion, in the absence of alcohol or of caustic alkali, between the molybdate and the phosphomolybdate compounds. It gave with the former in powder the brown oxide at once, in solution, a brownish precipitate, which appeared at once, or later, according
DETECTION OF PHOSPHORUS COMPOUNDS. 51
to the strength of the solution. On a solution of the molybdate containing nitric acid, c. g., that used as the reagent for phos- phoric acid, it had no apparent effect on the molybdenum com- pound, although, in a few minutes, a soluble, reddish, aromatic compound might be formed in the solution. On the other hand, with phosphomolybdates, either in the presence or in the absence of ammonium molybdate, or of nitric acid, or of both, it gave at once the dark green oxide of molybdenum.
Concerning the use of these reagents on tissues Macallum says: " On the molybdate and phosphomolybdate compounds distributed in animal and vegetable tissues, the phenylhydrazin hydrochloride acts as it does on these in the test-tube. It is not necessary to free the tissue preparations from ammonium molyb- date." He recommends washing the preparations for a minute or two in a dilute solution of nitric acid after which they are transferred to the reducing solution, which in less than two min- utes, brings out the green color where the phosphomolybdate compound occurs, but a faint yellow reaction where ammonium molybdate alone is present.
The technique of the reaction is as follows: Fresh tissues or tissues hardened in alcohol were used. Pieces of tissue or thin sections in the case of hardened material, were placed, for a period varying from ten minutes to forty-eight hours, in a solution of ammonium molybdate in nitric acid, prepared by dissolving one part of pure molybdic acid in four parts of strong ammonia, and adding thereto, slowly, fifteen parts of nitric acid, sp. gr. 1.2. After the nitric molybdate reagent has acted for a sufficient length of time, the preparations are washed in water or in dilute nitric acid, and treated with a ^ per cent, solution of phenyl- hydrazin hydrochloride, which reduces the phosphomolybdate to a -green-colored oxide of molybdenum.1 The tissues may be then dehydrated, cleared in. oil of cedar and mounted in balsam.
According to Macallum, inorganic compounds of phosphorus
'Although Macallum speaks of a green oxide of molybdenum being formed by this reaction, it is probable that the bodies formed belong to the blue oxides. The green color obtained at the beginning of the reduction of phosphomolybdate of ammonium in vitro is due to the yellow background of unreduced molybdate, that obtained in the tissues to the associated xanthoproteic reaction (vide infra).
52 R. K. BENSLEY.
are first affected, then lecithins, and finally the organic compounds of phosphorus. Where it is desired to demonstrate the distribu- tion of the latter he recommends the preliminary removal of the lecithins by repeated extraction with hot ethyl alcohol in a Soxhlet apparatus.
In the original form devised by Lilienfeld and Monti or in the form of Macallum's modification this reaction for phosphorus has been extensively employed. Macallum's original paper dealing with the reaction contains a considerable number of contributions dealing with the distribution of organic compounds of phosphorus in various tissues, and the reaction has been applied to the solu tion of special problems of this nature by Sherrington ('94), Gourlay ('94), Scott ('99), Held ('95), Bensley ('03), Wager ('05), Richter ('05), and many others. It is therefore of the utmost importance that every detail of the reaction should be carefully tested to exclude all possible sources of error.
Recently I have obtained results which have led me to suspect that the reaction obtained by Macallum's method is not wholly due to the formation in the tissue of ammonium phosphomolyb- date, but that other compounds of molybdenum may be present which are capable of reduction to the blue oxide by means of phenylhydrazin hydrochloride. For example, I observed that the peripheral portions of sections gave uniformly a deeper and more diffuse reaction than the central portions. This result was first noted in the tips of the villi in sections of the small intestine, and was ascribed to the presence of inorganic phosphates ab- sorbed from the food. Later it was noted that the same result was obtained in sections of the liver, pancreas, and other organs. Furthermore, I observed that freshly prepared solutions of the nitric molybdate often gave a strong reaction in the tissues after very short periods of immersion. For example, sections of the fundus region of the stomach of the rabbit, treated with warm, freshly prepared nitric molybdate reagent for ten minutes, then washed in water and reduced by means of a one per cent, solu- tion of phenylhydrazin hydrochloride gave a diffuse bluish green reaction together with a strong reaction in the nuclei and in the granules of the parietal cells. This result was clearly not due to phosphorus compounds of any sort, because the same nitric
DETECTION OF PHOSPHORUS COMPOUNDS. 53
molybdate reagent after having been kept several days, during which it had deposited copious crusts of molybdic acid, gave, when applied to sections from the same source, no such result, the reaction proceeding in the slow progressive manner character- istic of the phosphorus reaction as described by Macallum. Again, in his investigation of the nature of the 'granule cells of Paneth, Mr. Klein, working under my direction, found it neces- sary to employ formalin in the fixation of the tissues in order to preserve the granules. In preparations of this material treated by Macallum's method, we were surprised to obtain a strong reac- tion in the fibrils of the collagenic tissue of the tela submucosa.
Clearly, the intense marginal reaction obtained in sections and the early reaction obtained when freshly prepared solutions of the nitric molybdic reagent were used could not be due to phos- phorus. These anomalous characters of the reaction as applied to sections could only be explained on the assumption that, after the treatment with the nitric molybdic reagent, there existed in the tissue compounds of molybdenum other than phospho- molybdates, which gave the blue reaction with phenylhydrazin hydrochloride.
On account of the fact that the difference between freshly pre- pared and older solutions of the nitric molybdic reagent is to be found in the amount of molybdic acid contained, it seemed prob- able that the extraordinary results of the reaction, as described above, were due to the absorption of this substance by the tissue elements. Accordingly, I undertook experiments to determine the behavior of solutions of molybdic acid in reaction with phenylhydrazin hydrochloride, as well as the capacity of the tissue elements for absorbing it from its solutions. Later it was found necessary to reinvestigate the reaction obtained by treating ammonium molybdate in solution, and phosphomolybdate of ammonium suspended in water, respectively with solutions of phenylhydrazin hydrochloride.
Although the experiments were started with the expectation that a portion of the reaction would be found to be due to ab- sorbed molybdic acid, I still thought at that time that the funda- mental assumption was true, upon which the reaction was based, namely, that the organic phosphorus was liberated from its com-
54 R- R- BENSLEY.
binations by the reagent, converted into orthophosphoric acid and immediately precipitated in situ as ammonium phosphomolyb- date. As a result of the experiments, however, I have been forced to the conclusion that the whole of the reaction obtained by Macallum's method is due to compounds of molybdenum other than phosphomolybdate and that the phosphorus of the tissues is not concerned in the production of the reaction at all. For the purpose of testing the reactions of molybdic acid with phenylhydrazin hydrochloride, I prepared two soluble molybdic acids. The first of these was prepared by the method recom- mended by Ullik ('67). Barium molybdate, prepared by pre- cipitating a warm solution of ammonium molybdate with barium chloride washing thoroughly with hot distilled water, and dry- ing the precipitate on a water bath at 100° C., was suspended in water and decomposed with its equivalent of sulphuric acid. The solution was then filtered, tested for barium, sulphuric acid and chlorides, from which it was found to be free, and the total acidity was determined by titration with a normal solution of sodium hydroxide, using phenolphthalein as indicator. Assum- ing that the solutions contained a molybdic acid having the for- mula H2Mo2O7 the concentration of the solutions obtained by the method described above was in the case of one preparation 5.25 per cent., in another 7.52 per cent. The second molybdic acid was colloidal molybdic acid prepared by the process recommended by Graham (64), except that ammonium molybdate was employed instead of sodium molybdate. A solution of ammonium molyb- date in hydrochloric acid was dialyzed for several days against distilled water, until free from chloride. The resulting solution was then titrated against normal soda solution using phenolphtha- lein as indicator. According to Sabanejew ('90) the molecular weight of the molybdic acid prepared by Graham's method as determined by lowering of freezing point is 620 corresponding to the formula H2Mo4O13 . Assuming that the same compound was obtained by the dialysis of the solution of ammonium molyb- date in hydrochloric acid the solution obtained contained 6.73 per cent, of colloidal molybdic acid. From these solutions were prepared the various solutions mentioned in the succeeding ex- periments.
DETECTION OF PHOSPHORUS COMPOUNDS. 55
Solutions of both molybdic acids give, when treated with phenylhydrazin hydrochloride an immediate blue reaction which gradually deepens in color and a blue precipitate forms.
Sections of tissues fixed in alcohol, cut in paraffin, and fastened to the slide by the water method were placed in each of the solu- tions of molybdic acid. From time to time sections were re- moved from the solution, rinsed in water, and tested with a I per cent, solution of phenylhydrazin hydrochloride. It was found that the molybdic acid was taken up by the tissues from both solutions and was detectable in them by the blue reaction obtained by reduction with phenylhydrazin hydrochloride. In sections treated with pure solutions of soluble or of colloidal molybdic acid the strongest reaction was obtained in the collagenic fibrils which were deep blue. A slight diffuse reaction was obtained in the cytoplasm of cells, and a somewhat stronger reaction in the nuclear chromatin. The amount, however, of molybdic acid taken up from dilute pure solutions was not great except as regards the collagenic tissue. The experiments show, however, that molybdic acid may be taken up from its solutions by tissues and may be detected in these by the blue reaction produced by treatment of the sections with phenylhydrazin hydrochloride.
Under the conditions of the Lilienfeld-Monti-Macallum reaction molybdic acid occurs in the solution associated with nitric acid as well as with ammonium molybdate, ammonium nitrate, and the products of dissociation of all these compounds. Accordingly, the effect of the presence of acids on the absorption of the molybdic acid from its solutions by tissues was tested. Sections were placed in solutions of soluble and of colloidal molybdic acid to which five per cent, of nitric or of hydrochloric acid had been added, and were tested from time to time with phenylhydrazin hydrochloride. I found that the addition of either nitric acid or hydrochloric acid to the solutions of molybdic acid produced a remarkable increase in the capacity of sections for combining molybdic acid, which was again detectable by the blue or green reaction obtained by reduction with phenylhydrazin hydro- chloride. With the mixture of nitric and molybdic acids the reaction obtained after reduction was a deep greenish blue color in the nuclear chromatin, a faint greenish blue in the cytoplasm,
56 R. R. BENSLKY.
and a deep blue in the collagenic fibers. Except for the strong reaction in the connective tissue, the result obtained by treatment of sections with a solution of molybdic acid containing nitric acid, followed by reduction in one per cent, phenylhydrazin hydro- chloride was exactly similar to the so-called phosphorus reaction obtained by the procedure recommended by Macallum. It may be noted that the color obtained by the use of molybdic acid con- taining nitric acid followed by reduction differed from that pro- duced by reduction of molybdic acid by phenylhydrazin in the test tube, inasmuch as the former gives a greenish blue color, the latter a pure blue. This difference was obviously due to the yellow background afforded by the xanthoproteic reaction. As in the phosphorus reaction, the absorption of the molybdic acid was progressive, the reaction after eighteen hours being much stronger than after three hours.
Similar results were obtained with solutions of molybdic acid containing hydrochloric acid, except that the molybdic acid was taken up much more rapidly from the hydrochloric solution than from the nitric solution, and that the resulting reaction was blue rather than greenish blue, owing to the absence of the yellow zanthoproteic reaction. A further difference exhibited itself in the fact that sections left for some time in the solutions developed the blue color witJiout the use of any reducing' agent, the organic compounds of the tissue evidently acting as reducers. In the presence of nitric acid this, of course, could not occur because of the strong oxidative action of this compound.
Thus, in sections treated with solutions of molybdic acid con- taining either hydrochloric, or nitric acid, followed by phenyl- hydrazin hydrochloride, results were obtained which were the exact counterpart of the results of the so-called phosphorus reaction, although there could be little possibility of the form- ation of precipitates of ammonium phosphomolybdate in the tissues. Curiously enough, the anomalous characters occasion- ally observed in the reaction obtained by Macallum's method wene to be found in the molybdic acid material, that is to say, the more intense diffuse reaction of the outer portions of the sec- tions and the deep reaction in the connective tissue. It seemed clear from these experiments that a portion, at least, of the result
DETECTION OF PHOSPHORUS COMPOUNDS. 57
obtained by the procedure of Macallum was due to absorption of tnolybdic acid from the nitric molybdate solution. There was, however, some possibility that even this reaction with molybdic acid solutions depended on the presence of phosphorus and its liberation as phosphoric acid. It might be supposed that this phosphoric acid reacted with the molybdic acid to produce phosphomolybdic acid which was in turn precipitated by the albumens of the tissues. Or it might even be supposed that ammonium phosphomolybdate was formed, the ammonium ions necessary to the reaction being furnished by the albumens. That this is not the case, and that the reaction obtained by the use of molybdic acid solutions is in no way dependent on the phosphorus content of the tissue, I think the following experiments will show.
In studying the reaction of solutions of molybdic acid with phenylhydrazin hydrochloride, I found that the addition of nitric acid to the mixture retarded the reaction and if a sufficient quan- tity were present prevented it altogether. Accordingly, experi- ments were undertaken to determine the limits of this reaction with molybdic acid, ammonium molybdate, and ammonium phosphomolybdate, respectively, in the hope that a sufficient dif- ference in the behavior of these compounds would be discovered to enable one to employ a solution of phenylhydrazin hydro- chloride containing enough nitric acid to inhibit the reduction of molybdic acid and of ammonium molybdate while permitting the reduction of ammonium phosphomolybdate, and thus discrim- inate between these compounds occurring in tissues treated by Macallum's methods.
I found that with a constant concentration of phenylhydrazin hydrochloride, the amount of nitric acid required to prevent the reduction to the blue oxide of molybdenum varied directly with the concentration of the molybdic acid but was constant for any given concentration.
I found, moreover, that the blue reduction was invariably obtained in solutions of ammonium molybdate containing nitric acid, when they were treated with solutions of phenylhydrazin hydrochloride, provided the amount of nitric acid did not exceed a certain amount, which, as in the case of molybdic acid, was
58 R. R. BENSLEY.
constant for a given concentration of the other two constituents but varied directly with the concentration. This fact made it necessary to determine the conditions of this reaction with ammonium molybdate if solutions of the hydrochloride con- taining nitric acid were to be used for the reduction of the sec- tions, because in trying to eliminate the reduction of the molybdic acid by using a solution of the hydrochloride containing nitric acid, a new source of error might be introduced, inasmuch as the nitric acid would make ammonium molybdate available to the blue reduction.
The experiments to determine the limits of these reactions were made in test-tubes in much the same way as experiments in haemolysis are carried out. In each of a series of test-tubes was placed, from a pipette graduated in fiftieths of a cubic centi- meter, a measured quantity of the solution of molybdic acid. To this was added a quantity of nitric acid solution of known strength increasing by increments of one tenth of a cubic centi- meter from tube to tube. Sufficient distilled water was then added to make the contents of each tube up to 9. 5 c.c., and finally 0.5 c.c. of a two per cent, solution of phenylhydrazin hydro- chloride was added to each tube. In such a series of tubes, if a sufficient range of concentrations of the nitric acid was included the tubes at one end of the series would give the blue reduction, those at the other would at first show no signs of reaction, but after several hours would develop a brownish color. At some point in the series two tubes, side by side, differing from one another only in the nitric acid content, would present the one a blue, the other a brown color. When solutions of nitric acid containing 32 grammes of nitric acid per looc.c. were employed, that is, when the difference in the contents of two tubes amounted to .032 gr. of nitric acid, the contrast in color between the tubes which marked the limit of the reaction was a very striking one. Attempts to define this limit more accurately by the use of more dilute solutions of nitric acid, and accordingly smaller increments, of nitric acid from tube to tube did not result more satisfactorily. For example in a series of tubes in which the increment of nitric acid was 0.012 gr. from tube to tube, the transition was distrib- uted over several tubes, those immediately preceding the first
DETECTION OF PHOSPHORUS COMPOUNDS. 59
tube free from the blue precipitate containing a slight blue pre- cipitate which subsided after several hours leaving a brownish supernatant fluid. Thus, the possible error in determining the proportion of nitric acid necessary to prevent the blue reaction is considerable, although the results are accurate enough for the purposes of this investigation, as subsequent statements will show.
REACTIONS OF SOLUBLE MOLYBDIC ACID WITH PHENYL-
HYDRAZIN HYDROCHLORIDE IN THE PRESENCE
OF NITRIC ACID.
Percentage of Phenyl- Percentage of Nitric
Strength of Molybdic Acid hydrazin Hydro- Acid Necessary to Pre-
in Fractions of Ncrmal. chloride. vent Blue Reaction.
O.O2 O.I 1.38
0.04 o.i 2.26
0.06 o.i 2.94
0.08 o.i 3.27
REACTIONS OF SOLUTIONS OF AMMONIUM MOLYBDATE WITH PHENYLHYDRAZIN HYDROCHLORIDE IN THE PRESENCE
OF NITRIC ACID.
Solutions of ammonium molybdate when treated with phenyl- hydrazin hydrochloride give, as stated by Macallum, a brown color, and a brown precipitate slowly forms in the solution. In the presence of nitric acid, however, provided the latter does not exceed a certain amount which varies with the concentration of the molybdate, the reaction consists in the production first of a blue color and finally of a deep blue precipitate. If the amount of nitric acid exceeds this maximum no reaction occurs at first, but a brown color slowly develops in the solution. The follow- ing table gives the concentration of nitric acid necessary to pre- vent wholly the blue reaction with several concentrations of molybdate.
Percentage of Ammonium Percentage of Phenylhydrazin Per Cent. Nitric Necessary to
Molybdate. Hydrochlotide. Prevent Blue Reaction.
0.5 o.i 3.14
I.O O.I 4.40
1.5 o.i 5.03
2.0 O.I 5.66
6O R. R. BENSLEY.
REACTIONS OF PHOSPHOMOLVBDIC ACID AND PHOSPHOMOLYB- DATE OF AMMONIUM WITH PHENYLHYDRAZIN HYDROCHLORIDE.
Phenylhydrazin when added to a solution of phosphomolybdic acid or to crystals of ammonium phosphomolybdate suspended in water gives at once the reduction to the blue oxide. The reac- tion under these conditions proceeds so rapidly that it is difficult to follow the steps. The resulting body is not green in color as described by Macallum but blue, the green color which is first seen when phenylhydrazin hydrochloride is added to the crystals of ammonium phosphomolybdate being simply due to the yellow background afforded by the unreduced phosphomolybdate. After a few minutes the reaction proceeds still further and a solu- ble blue-violet compound is formed.
In the presence of nitric acid, the reaction proceeds somewhat more slowly, although it is less sensitive to the presence of nitric acid than the corresponding reactions with molybdic acid and ammonium molybdate. With crystals of phosphomolybdate sus- pended in water and o. I per cent, of phenylhydrazin the concen- tration of nitric acid may be increased to 36 per cent, without the reduction to the blue oxide being prevented. Even in the pres- ence of this great amount of nitric acid the reduction of the phosphomolybdate reaches a maximum within ten minutes after the phenylhydrazin hydrochloride is added. The reaction between phenylhydrazin and phosphomolybdic acid proceeds in much the same way, and is similarly much less sensitive to the presence of nitric acid, than the corresponding reactions with molybdic acid and ammonium molybdate. For purposes of comparison the experiments were made the results of which are presented in the subjoined table.
Percentage of Phosphomolyb- Percentage of Phenylhydrazin Per Cent. Nitric Acid Necessary die Acid. Hydrochloride. to Prevent Blue Reaction.
o.i o.i 6.55
O.2 O.I 9.82
0.3 o.i 13.10
0.4 o.i J4-74
On comparison of this table with the preceding one it will be seen that the reduction of phosphomolybdic acid having a con-
DETECTION OF PHOSPHORUS COMPOUNDS. 6 1
centration of o. I per cent, will proceed in the presence of nitric acid having a concentration sufficient to prevent reduction in a solution of ammonium molybdate of 2 per cent, strength.
While it would have been difficult to draw from these experi- ments conclusions as to the probable behavior of the compounds of molybdic acid in the tissues when treated with solutions of phenylhydrazin hydrochloride containing nitric acid, yet they suggested a possibility which was capable of being proved experi- mentally that the compounds of molybdic acid and molybdates found in the tissues would fail to react to phenylhydrazin hydro- chloride in the presence of an amount of nitric acid which would have no effect on the reduction of ammonium phosphomolybdate.
In order to test this question, sections of the liver of Necturus prepared after fixation in alcohol and fastened to the slide by the water method were treated with Macallum's nitric molybdate re- agent, a solution of soluble molybdic acid in 10 per cent, nitric acid, and a ten percent, solution of phosphoric acid, respectively. The two first mentioned solutions were allowed to act for three hours at 37.5° C. followed by eighteen hours at ordinary room temperature. They were then tested with a o. I per cent, solution of phenylhydrazin hydrochloride and found in each case to give a strong reaction corresponding in its characters and distribution to the phosphorus reaction of Macallum. The reaction obtained in the sections treated with the solution of molybdic acid was much the stronger. Other sections from the same lot were then treated with solutions containing o. I per cent, of phenylhydrazin hydro- chloride and varying known quantities of nitric acid, in each case for a period of fifteen minutes. The sections from the molybdic acid solution and from the nitric molybdate reagent were treated side by side in the same solution, and for purposes of control a section which had been soaked in phosphoric acid and then treated with the nitric molybdate reagent was also put at the same time in the solution, so that it was possible to observe the effect of different concentrations of nitric acid on the reduction of sections treated with molybdic acid, or with the nitric molybdate reagent, and of sections containing ammonium phosphomolybdate arti- ficially introduced. It was my expectation that a low concentra- tion of nitric acid would suffice to abolish that portion of the reac-
62 R. R. BENSLEY.
tion which was due to ammonium molybdateand to molybdic acid, and that a considerable residuum of the reaction would be found unaffected by even high concentrations of nitric acid and could thus be interpreted as a true phosphorus reaction. I was quite un- prepared for, and greatly disappointed at the actual result of these experiments, namely, that relatively low concentrations of nitric acid abolished the reaction altogether.
With a concentration of 3.27 per cent, of nitric acid, phenyl- hydrazin hydrochloride o.i per cent., the molybdic acid sections and the nitric molybdate section showed no reaction after three minutes' treatment, although the section containing ammonium phosphornolybdate artificially introduced gave a maximum reac- tion in less than one minute. After fifteen minutes' action, a very faint reaction was obtained in the nuclei, both in the mo- lybdic acid section and in the nitric molybdate section. When the concentration of the nitric acid reached 16.37 Per cent., the phenylhydrazin remaining the same, the reaction was not recog- nizable after fifteen minutes' treatment although sections contain- ing ammonium phosphomolybdate artificially introduced reduced to a maximum depth of color in the same solution in five minutes. I have repeated these experiments many times, always with the same results. It is significant that the reaction disappeared at exactly the same point as regards concentration of nitric acid in the molybdic acid section and the nitric molybdate section.
Only one conclusion is possible from these experiments, namely, that sections after treatment with Macallum's reagent for this length of time did not contain appreciable quantities of ammonium phosphomolybdate. Thus the fundamental assump- tion on which the reaction of Lilienfeld and Monti and of Macal- lum is based falls to the ground. It is obvious that if the phos- phorus of the organic compounds is liberated at a point short of the destruction of the recognizable structures of the cell, it is not, at all events, precipitated in situ by the nitric molybdate reagent.
As a result of these experiments I am of the opinion that the reaction obtained by Macallum's procedure is entirely due to the formation of compounds of molybdic acid with the albumens of the tissue and not in any respect to the formation of ammonium phosphomolybdate at the expense of the organic phosphorus.
DETECTION OF PHOSPHORUS COMPOUNDS. 63
The facts on which the conclusion is based are, briefly, as follows :
The essential conditions of a successful phosphorus reaction are, first, that the phosphorus may be liberated from its organic combinations at a point short of the destruction of the recogniz- able structure of the cell ; second, that the liberated phosphorus be precipitated at once at the point of origin as ammonium phos- phomolybdate ; third, that the reducing substance employed to make the phosphomolybdate visible for microscopic study act on phosphomolybdate and on no other compound of molybdenum which may be present in the tissue.
Phenylhydrazin hydrochloride does not meet the third condition because it reduces to the blue oxide of molybdenum, soluble molybdic acid in the test tube as well as molybdic acid combined with the tissue constituents in sections.
Phenylhydrazin hydrochloride also produces the blue oxide when treated with ammonium molybdate in the presence of nitric acid, provided that the latter does not exceed a certain concen- tration which is constant for constant concentrations of the mo- lybdate.
Nitric acid affects the reduction of molybdic acid, ammonium molybdate, and ammonium phosphomolybdate, by phenylhydra- zin hydrochloride in the same way, namely, retards the reduc- tion, but to different degrees, inasmuch as low concentrations of nitric acid prevent the reduction of the two former to the blue oxide, while high concentrations of nitric merely retard the blue reduction of the phosphomolybdate. Accordingly, if phospho- molybdate is formed at the site where a reaction is obtained by the method of Macallum, the reaction ought to be elicited by treat- ment of the sections with solutions of phenylhydrazin in having a high content of nitric acid. This, however, the experiments show is not the case. Even low concentrations of nitric acid eliminate the greater portion of the reaction, and the reaction is entirely abolished by a nitric acid content which has little effect on the reduction of phosphomolybdate of ammonium artificially introduced into sections for purposes of control. Furthermore, the reaction is abolished at the same concentration of nitric acid with sections treated with Macallum's nitric molybdate reagent
64 R. R. BENSLEY.
as with sections treated with a pure solution of molybdic acid. These facts dispose finally of the first and second essential con- ditions of a successful microchemical reaction for organic phos- phorus, for it is clear that if the sections after treatment with the reagent contain no phosphomolybdate of ammonium, that the organic phosphorus has either not been liberated from its compounds, or that, if it has, it has not been precipitated at the moment and at the point of liberation. If these conclu- sions are correct, it is also obvious that there is no hope of a real phosphorus microchemical reaction being obtained by the employment of the nitric molybdate reagent.
These conclusions do not, of course, apply to the identifica- tion of phosphates by the nitric molybdate reagent, in cases where the characteristic crystal form of the ammonium phospho- molybdate can be recognized under the microscope.
In conclusion, it may be mentioned that in making the experi- ments to determine the effect of nitric acid on the reduction of the molybdenum compounds by phenylhydrazin hydrochloride it is important to employ solutions which are free from nitrous acid, which reacts with the phenylhydrazin and reduces its con- centration.
BIBLIOGRAPHY.
Bensley, R. R.
'03 The Structure of the Glands of Brunner. The Decennial Publications, Uni- versity of Chicago, Vol. X., 1903, pp. 279-326.
Gourlay, F.
'94 Proteids of the 1'hyroid and Spleen. J. Physiol., Cambridge, Vol. 16,1894,
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'64 On the Properties of Silicic Acid and other Analogous Colloidal Substances. J. Chem. Soc., Lond., n. s., Vol. 2, 1864, pp. 318-327.
Heine, L.
'96 Ueber die Molybdansaure als mikroskopisches Reagenz. Ztschr. f. physiol. Chem., Strassburg, Bd. 22, 1896-97, pp. 132-136.
Held, H.
'95 Beitrage zur Structur der Nervenzellen undihrer Fortsatze. Arch. f. Anal. u. Entwicklngsgesch., Leipzig, 1895, pp. 396-414.
DETECTION OF PHOSPHORUS COMPOUNDS. 65
Lilienfeld, L., u. Monti, A.
'93 Ueber die mikrochemische Lokalisation des Phosphors. Ztschr. f. physiol.
Chem., Strass., Bd. 17, 1893, pp. 410-425. Macallum, A. B.
'98 On the Detection and Localization of Phosphorus in Animal and Vegetable Tissues. Proc. Roy. Soc., Lond., Vol. 63, 1898, pp. 467-479.
Polacci, G.
'94 Sulla distributzione del fosforo nei tessuti vegetali. Malpighia, Vol. 8, 1894,
PP- 36I-379- Raciborski, M.
'93 Review of Lilienfeld and Monti's Article (vide supra). Botanische Zeitung, Jahr. 51, 1893, pp. 245-247.
Richter, 0.
'05 Die Fortschritte der botanischen Mikrochemie seit Zimmermanns Botanischer Mikrotechnik. Ztschr. f. wissensch. Mlkr., Leipz., 1905, Bd. 22, pp. 194- 261.
Sabanejew.
'90 Quoted after abstract in Ber. d. deutsch. Chem. Gesellsch., Berl., 1890, Bd. 23, Referate, p. 87.
Scott, F. H.
'99 The Structure, Michrochemistry and Development of Nerve Cells. Tr.
Canad. Inst., Toronto, Vol. 5, 1899, PP- 4°5~433- Sherrington, C. S.
'94 Note on some Changes in the Blood of the general Circulation consequent upon certain Inflammations of acute and local Character. Proc. Roy. Soc., Lond., Vol. 55, 1894, pp. 161.
Ullik, F.
'67 Untersuchungen iiber Molybdansaure und deren Salze. Annalen d. Chem. u.
Pharm. herausg. v. Wohler, Liebig, u. Kopp, Heidelb. , Bd. 144, 1867, pp.
320-351- '70 Ueber Molybdansaure und ihre Verbindungen. Ibid., Bd. 153, 1870, pp.
369-376. Wager, H.
'05 On some Problems of Cell Structure and Physiology. Sectional Address,
Section K, Botany, British Association for the Advancement of Science,
English Mechanic and World of Science, No. 2111, 1905, pp. 102-108.
ON THE LOCOMOTION OF A SEA ANEMONE (METRIDIUM MARGINATUM).1
J. F. McCLENDON.
Last winter while studying some animals in the marine aquaria of the University of Pennsylvania I noticed that the anemones, after being placed at the bottom of an aquarium, would creep up the side of the glass to a more favorable position. Their method of progression is similar to the ordinary creeping of a snail,2 con-
FlG. I. AL'tridiiun inai^ino/iini seen through the glass, up which it is creeping. The lower side of the photograph has been outlined.
sisting of a succession of waves that travel from behind forward, but in the anemone the waves are larger and not so rapid or regular. The accompanying photographs were taken of an anemone creeping up the side of an aquarium, with its distal end inclined forward, probably to test the water into which it was advancing. The undulations of the foot progress in the direction of locomotion. If the functionally posterior end of the
1 Contribution from the Zoological Laboratory of the University of Pennsylvania.
2 For a more complicated form of locomotion in some snails see A. J. Carlson : "The Physiology of Locomotion in Gasteropods," BIOL. BULL., Vol. 2, January
1905, pp. 85-93.
66
LOCOMOTION OF A SEA ANEMONE. 67
foot be watched closely it will be seen to let go at several points (below in Fig. i ) and slip forward. This contraction is carried forward and on reaching the center of the foot, the contracted portion rises up from the glass, forming a wave that deepens as
FlG. 2. Metridiiim marginatum about half a minute later than Fig. I.
it approaches the "anterior" end (Fig. 2, above). On reaching the " anterior " edge the wave is retarded by the firmer attachment of the edge, which releases locally, breaking the wave into seg- ments (Fig. i, above). A wave requires about a minute to trav- erse the foot of the anemone, and before it has disappeared, another commences.
I threw a number of anemones into an aquarium to observe their actions. They threw out acontia, which caught hold of any solid near them and contracted until some portion of the foot touched the object and caught hold. One anemone sinking to the bottom and resting on its tentacles contrived to rierht itself
o
by suddenly contracting and expelling water from its mouth. I observed this once or twice subsequently, but rather think it a coincidence than a common reflex.
BIOLOGICAL HALL, UNIV. OF PENN., December 5, 1905.
THE SIGNIFICANCE OF SCUTE AND PLATE "ABNORMALITIES"1 IN CHELONIA.
A CONTRIBUTION TO THE EVOLUTIONARY HISTORY OF THE CHELONIAN CARAPACE AND PLASTRON.
H. H. NEWMAN. CONTENTS.
PART I.
PAGE. I. Introduction.
1. Statement of the Problem 68
2. Nomenclature. The Normal Plate and Scute Pattern: (a) Plates;
(/;) Scutes 69
II. Discussion of the Present Status of the Question Concerning the Morph- ology of the Chelonian Armor.
1. Paleontological Data 71
2. Embryological Data 72
3. Data Derived from Comparative Anatomy 74
III. Description and Discussion of Abnormalities.
1. Inframarginals 77
2 . In terpl astrals 80
3. Supernumerary Scutes in a Row on the Carapace 81
4. Supernumerary Scutes in a Row on the Plastron 93
5. Correlated Abnormalities in Scutes and Bony Plates, with Discussion
Regarding the Relationship Between these Two Structures 94
6. Correlation in Scute Abnormalities 9&
I. INTRODUCTION.
I . Statement of the Problem.
During a residence of several years on Lake Maxinkuckee, Marshall County, Indiana, my attention was repeatedly attracted to the large numbers and variety of species of tortoises that are found in the lake and in its accessory streams, swamps and pools.
In the spring of 1903 I began a study of the habits, variations,
'The word "abnormalities" in the title is used for lack of a better one, and includes supernumerary scutes and plates, deficiencies in these structures and cases of fusion. The word " diversities " might have been used with equal appropriateness.
68
"ABNORMALITIES" IN CHELONIA. 69
etc., of these species, involving the collection of large numbers of individuals of all sizes. One of the most striking phenomena that came to light was the prevalence of many kinds of scute abnormalities, consisting for the most part of supernumary scutes on the carapace and plastron. As examples multiplied I became aware of a marked degree of regularity in these abnormalities, the same supernumerary scutes occurring in exactly the same locations time after time.
Diversity in scutes had been noted by two observers. Gadow ('99) studied Tlialassochelys carctta (L.), a species with no fixed number or arrangement of scutes, and Parker ('01) found two abnormal specimens of Chelopus insculptus (Le C.) on the basis of which he published a paper on correlated abnormalities in the scutes and the bony plates.
It seemed, then, that this phenomenon needed further investi- gation and the collection of large numbers of abnormal speci- mens was begun in the hope of reaching a rational explanation of this very prevalent diversity. Careful study has convinced me that these abnormalities are to be considered not as meaning- less anomalies but as examples of systematic atavism in the sense of deVries. From this standpoint it seems possible to throw some light on the phylogeny of Chclonia.
The color patterns are intimately associated with the scutes and throw much light on their phylogeny. Consequently a brief consideration of chelonian coloration has been appended.
2. Nomenclature. The Normal Plate and Scute Pattern.
The following description and appended drawings (Plate I., Figs, i and 2), although referring particularly to an adult female specimen of Graptemys geographica, will apply to any genus of the Emydidae. Fig. I represents the dorsal and Fig. 2 the ventral aspect.
The armor of tortoises consists of two elements, bony plates and horny scutes, which for brevity will be referred to as plates and scutes. Dotted outlines are used for the plates and solid outlines for the scutes. In labeling, small letters are used for plates and capital letters for scutes.
A. Plates. — There are in the carapace (Fig. i) five longitudinal
7O H. H. NEWMAN.
rows of plates, a single median and two paired rows. The median row has been variously designated as dorsal, vertebral and neural. In this paper the term neural will be invariably used. The neural row consists of the following elements : an anterior plate of large size called the nuchal (;/?/.), eight neurals (n. i-S), two procaudals (pr. I and 2), and posteriorly the pygal (/>.).
Lateral to the median row are the paired costals (c. I— 8), directly overlying the eight pairs of ribs.
Bordering the carapace on both sides and extending from nuchal to pygal are the marginals (;//. i — 1 1).
The plates of the plastron (Fig. 2) are nine in number — the paired epi- (V.), hyo- (ho.}, hypo- (hp.}, and xiphi- (.r.) plastrals, and the unpaired endo-plastral (en.}.
The hyo- and hypoplastrals articulate directly with the fourth, fifth and sixth marginals and form the so-called " bridge ' be- tween the dorsal and ventral armor.
B. Scutes. - - On the carapace (Fig. i) there are, as in the case of the plates, five longitudinal rows of scutes that receive the same names as the plates. The median row, neurals, consists of a small anterior element, the nuchal (NU.}, and five large neurals (N. 1-5). There are four pairs of large costals (C. 1-4). Twelve pairs of marginals (M. 1 — 12) completely surround the carapace with the exception of the small space occupied by the nuchal.
The scutes of the plastron (Fig. 2) are twelve in number, con- sisting of six pairs of large flat elements named from anterior to posterior end as follows : gulars (6".), numerals (H.}, pectorals (P.}, abdominals (A.}, femorals (F}, and anals (AN}.
At the angles made by the junction of the pectorals and ab- dominals with the marginals are two pairs of small triangular scutes called respectively axillaries (A^.) and inguinals (/.). These constitute all that remains in the Emydidae of the inframarginals, a row much more prominent and complete in more primitive families.
No other plates or scutes occur normally among the Emydidae, but for the sake of completing the nomenclature, it should be mentioned that one species, Macrochelys teunnincki, possesses an additional pair of rows of scutes between costals and marginals,
ABNORMALITIES IN CHELONIA. /I
called SHpraiiMrginals. Traces of a median ventral row of scutes are found normally in some species - - and I have given the name " inter pldstral* to this row. A single median scute occurs normally in the anterior part of the plastron of certain special- ized groups and receives the name intergular.
II. DISCUSSIONS OF THE PRESENT STATUS OF THE QUESTION CONCERNING THE MORPHOLOGY OF THE CHELONIAN ARMOR.
The frequent abnormal occurrence of traces of the inframargi- nals and interplastrals in Grapteinys gcograpliica, Chryscinys mar- gi/iataznd Chclydra scrpcntinaled me to review the literature re- lating to the evolutionary history of the chelonian carapace and plastron.
For nearly a century the chelonian armor has offered to mor- phologists a problem of unusual difficulty, and, although much has been written on the subject, its derivation is still unsettled. The question has been attacked from the three standpoints of paleontology, embryology and comparative anatomy.
I. Paleontological data are far from conclusive. It is not pos- sible to go into this phase of the subject at all fully. Baur in 1887 published a brief summary of the more valuable paleonto- logical data in an article entitled " On the Morphogeny of the Carapace of the Testudinata." A brief statement of the substance of this paper will, perhaps, serve to show the inadequacy of the paleontological evidence in this case.
The condition seen in the Dermochelydae is considered to be the most primitive. Fossil remains of this gro^ip agree closely with the existing Dermochelys coriacca in the possession of " a pavement of small osseous plates extending over the whole shield, jointed to one another by more or less fine sutures. The num- ber of these plates is much larger than that of the other Testudi- nata, which is never more than 70." This pavement of osseous plates is not united with the internal skeleton, as are the plates of other Testudinata, but has an independent dermal origin. " That the carapace of the Dermochelydae is homologous to the carapace, without internal skeleton, of the rest of the Testudinata, there is no doubt." The fusion of the dermal pavement bones with the ribs and vertebras is, according to Baur, proved by a
72 H. H. NEWMAN.
specimen of Eretnwclielys imbricata, a fossil species in which are found " small polygonal plates of the same shape as those of Dermochelys, suturally connected with the third, fourth, fifth and sixth costal plates." "A form between the Dermochelydae and " Thecop/iora" (Dollo) is represented by the oldest known turtle, Psephodenna alpinuin, H. v. Meyer, from the Triassic of the Bavarian mountains, preserved in Munich. In this highly in- teresting specimen, never mentioned in monographs on the Testudinata, we have certainly not less than 193 plates suturally united." According to Zittel's Paleontologie, Baur later ex- pressed the opinion that Psephodenna may not be a chelonian at all, but perhaps a nothosaurus. Thus doubt is cast upon the best link in the chain of evidence. That all the principal groups of Chelonia were in existence in the earlier Mesozoic ages and that Palaeozoic Chelonia are entirely unknown are familiar facts. So our attempts to reconstruct an ancestral condition must be made largely on the basis of embryology and compara- tive anatomy.
2. Nor is cinbryological evidence of chelonian phylogeny at all conclusive. The best and most recent study of the develop- mental history of the chelonian carapace and plastron was made by Goette in 1899. He summarizes the previous literature on the subject and shows that the main question at issue is that of the character of the neural and costal plates. Some authors, principally paleontologists, have maintained that these structures have a dermal origin and hence arise independently of the inter- nal skeleton. Others hold that these plates are mere outgrowths of the ribs and spinal processes of the vertebras. Goette favors the latter view and presents as evidence of its correctness a series of very careful embryological studies.
Suspecting that there might be some flaw in Goette's work, I repeated much of it, using the embryos of Chelydra serpcntina and Grapteinys geograpJiica, and have satisfied myself that the neural and costal plates actually do originate as outgrowths of a differentiated tissue that surrounds the neural and rib cartilages. Whether this differentiated tissue be true periosteum, as Goette affirms, or simply a somewhat denser portion of the connective tissue that fills the space between the epidermis and the cartilagi-
ABNORMALITIES IN CHELONIA. 73
nous skeleton, is not certain. Haycraft ('99) maintains the lat- ter view, but his paper is far from convincing.
As to the remaining plates of the carapace — nuchal, pro- caudals, pygal and marginals — there is no difference of opinion. All agree that they are of true dermal origin.
Thus it would seem that the plates of the carapace have a dual origin — the neurals and costals being periosteal ossifications while the nuchal, procaudals, pygal and marginals are dermal ossifications.
The carapace, then, as it exists to-day is not a simple struc- ture but consists of a complex of at least two independent systems of bones.
Accepting the evidence of embryology as to the origin of the neural and costal plates, it remains to determine whether the dermal ossifications are, as Goette believes, mere supplementary structures that have come in to supply the deficiencies of the periosteal system, or are remnants of a once more or less complete dermal carapace that has in large measure been rendered super- fluous by the broadening-out of the ribs and neural processes. The latter view would involve the former existence of complete rows of dermal bones overlying the vertebrae and ribs. Embry- ological evidence seems contrary to this view, as no dermal ossi- fications are found in the costal or mid-neural regions. It is possible that we may in this case overestimate the evidence of embryology as a guide to phytogeny. The great antiquity of the chelonian carapace is undoubted and in highly specialized structures that have attained a marked morphological fixity we should not be surprised to find great condensation in develop- ment, so that two structures formerly independent in origin — such as dermal and periosteal plates — may originate simulta- neously so as to form only one inseparable structure. It seems quite plausible, then, that the rapid secondary broadening of ribs and neural processes has crowded out or appropriated the primordia that formerly went to form the dermal carapace and that only in places where the ribs and neural processes fail to reach the dermis do the true dermal bones have a chance to appear.
1 he fact that the nuchal plate appears before the ribs and
74 H. H. NEWMAN.
neural spines have even commenced to broaden out and that the procaudals and the marginals follow before the neurals and costals are completely organized, points to the antiquity of these dermal structures and indicates that the neurals and costals are of more recent origin.
3. Comparative anatomy furnishes us much valuable evidence. In the family Trionychidae, for example, we have a series of forms that show a gradual reduction of a portion of the dermal armor. Fossil Trionychidae are well known in which are shown a nuchal, a procaudal and a nearly complete set of marginal plates. Such a form was figured by Dollo in 1884 and named by him Pseudotrionyx. Another fossil species discovered by the same palaeontologist and named by him Emyda granosa, lacks the procaudal and the marginals from the anterior half of the carapace. A third form, Emyda Ceylonemis, possesses a nuchal and several marginals at the posterior part of the carapace. The extreme limit of reduction is seen in Aspidonectes spiuifcr, which possesses only the nuchal plate as the last remnant of the dermal carapace.
It will be noted that the order of the appearance of these dermal ossifications in ontogeny is just the inverse of the order of disappearance in phylogeny. The latest elements to be formed in ontogeny are the first to disappear in phylogeny. This is just what we would expect if we consider that there has been a gradual shortening of the developmental process, a gradual elimination of the latest stages. The Trionychidae show clearly that there is a marked tendency to reduce the system of dermal bones and it is not difficult to imagine that earlier reduction has taken place in which the dermal ossifications of midneural and costal regions were lost.
What evidence have we that such dermal ossifications over- lying neural processes and ribs actually existed ? O. P. Hay ('97) in an important paper dealing with the evolution of the chelonian carapace and plastron, describes and pictures an in- complete carapace of a fossil form named Toxochelys serrifer. Three ossicles occur above and overlapping the neural plates and occupy positions coincident with the keels of the second, third and fourth neural scutes. These ossicles have the general form
"ABNORMALITIES" IN CHELONIA. 75
of the tubercles seen on the dorsal ridge of the tail of Clielydra scrpcntina, and this suggests that the ossicles of Toxochelys are merely a continuation forward of a series of tubercles that must have been present on the tail.
Hay suggests that the keels seen especially in the young of modern Chdonia are the representatives of ancient dermal tuber- cles that formed the chief armor of ancestral forms. That in most cases these dermal ossicles have ceased to form indepen- dently of the deeper and more vigorous bony layers is perhaps to be expected as the result of condensation in developmental processes.
The degree to which modern species exhibit keels is extremely varied. Some highly specialized forms show none, or at most one, even in very young specimens, while one very primitive spe- cies, Macrochclys tcmmincki, possesses seven distinct keels on the carapace and four rows of flat scutes on the plastron. This mul- tiplicity of keels is evidently a very primitive condition and natu- rally suggests to Hay the condition seen in Dermochelys coriacea in which twele well-marked keels are found, each keel consist- ing of rows of dermal ossifications that are lager and more prominent than the remaining intermediate ossicles that form the continuous pavement of the test. This peculiar aberrant che- lonian is taken by Hay, following Baur and others, as the hypo- thetical ancestral type from which our modern chelonians have been derived by a process of simplification.
A survey of the field reveals the fact that the nearest approach to this condition of twelve rows of keels is seen in Macrochelys tcmmincki, which possesses seven distinct keels on the carapace. The four rows of flat scutes on the plastron may once have been keeled, for keels on the plastron are known in both extinct and living groups. The total number of keels or keel equivalents in Macrochelys is then eleven, one short of the supposed ancestral condition. The missing keel is the mid-ventral one and is repre- sented in certain groups by intergulars. Thus all of the ancestral keels find representatives among modern species.
Hay seems to have been the first observer to suggest the im- portance of the scutes as factors in the evolution of the carapace. Previous authors have confined their attention to the bony struc-
76 H. H. NEWMAN.
tures, considering the scutes as of little significance. Hay's view of the role of the scutes may be stated briefly as follows : The probable ancestral condition is that seen in Dermachelys, the skin of which is found to be broken up into small polygonal areas, larger in the keels than elsewhere. These areas coincided with the osteodermal plates that are or will be developed in the skin. As the deeper elements of the carapace (neural and costal plates) increased in protective efficiency, the dermal structures were in many regions rendered superfluous and disappeared. In some cases the scutes were lost with their corresponding plates, in others the lost plate left its trace in the keel of the scute. The direction of growth of each of the existing series of scutes shows the direction of encroachment on other rows now lost.
This exposition of Hay's seems to me to be the most rational yet advanced, yet I believe that he fails to appreciate the evidence of embryology and thus introduces undue complexity. In the first place, he considers the nuchal plate as a fascia bone instead of an ordinary dermal plate. In the second place he states that the neural and costal plates are of the same character as the nuchal. Embryology shows that the nuchal plate is as true a dermal bone as are the marginals, while the neurals and costals are true periosteal expansions. It seems to me more rational to suppose that the dermal ossifications of the mid-neural and costal regions have undergone a complete suppression identical with that indicated by the series of Trionychidae described above, rather than that they have become indistinguishable by fusion with the rib and neural fascia bones, as Hay calls them.
If we remove the scutes and underlying dermis from the cara- pace of a specimen of CJielydra we find that the long tubercles on the neural and costal plates bear no constant relation to the plates themselves, but are nevertheless clearly of a piece with them. It was natural for Hay to suppose that these bony tubercles were produced separately and then fused with the underlying plates. I have been able to trace this matter to a conclusion in the young of Chclydra, with the result that I have seen all the stages of ossification in the carapace and know that the tubercular keels on the neural and costal plates are produced by gradual thickenings of the growing plates. These thickenings
"ABNORMALITIES IN CHELONIA. 77
send out branching processes that gradually displace the dermal connective tissue of the tubercles and fill the space with bone. Complete ossification of these tubercles does not occur until the animals are several years of age.
III. DESCRIPTION AND DISCUSSION OF ABNORMALITIES.
That a process of reduction both in the number of rows of scutes and in the number of scutes in surviving rows has taken place seems highly probable. From this standpoint I made a systematic study of all the abnormal specimens that showed traces of these lost rows or lost scutes. Inframarginals of all grades of prominence were found in specimens of Graptcmys geograpkica and Chrysemys marginata, while interplastrals were found more rarely in the same two species. It will be noted that both of these recurring rows are plastron rows which probably means that the carapace has reached a high degree of fixity with refer- ence to number of rows. Yet many abnormalities are found that indicate that the reduction in the number of scutes in a row was of comparatively recent occurrence.
These abnormalities will be discussed under three heads : (i) Inframarginals, (2) interplastrals, (3) supernumerary scutes in a
row.
i . Inframarginals.
The occurrence or non-occurrence of inframarginals has formed the basis for separating the Thecophora into two great groups. Gadow in his volume on Amphibia and Reptiles gives Boulanger's key for classifying Chelonia. In this the two groups are charac- terized as follows :
1. Pectoral shields separated from the marginals by inframar- ginals— Chelydridae, Platysternidae, Cinosternidae.
2. Pectoral shields in contact with the marginals — Testudini- dae, Chelydidas, Pelomedusidae.
It is evident that the more primitive families possess as normal factors this row of scutes while the more specialized families normally lack this row. When, however, dozens of specimens of Graptcmys and Chrysemys possess this row in more or less perfect form, I am forced to consider this phenomenon as a well- marked case of systematic atavism. In view of the fact that no
78 H. H. NEWMAN.
such anomalies have been previously described, it seems worth while to tabulate those in my collection - - an easy task in view of the fact that the scutes occur in definite places. In any species, such as Chelydra, that possesses this row normally, there are typically three scutes in the row, one in contact with the axillary, one at the angle of contact of the pectoral and humeral and the marginals, and one abutting on the inguinal scute. These three scutes may be designated respectively as I., II. and III. Out of 476 specimens of Grapteuiys geographica examined, I found 3 1 with traces of inframarginals varying all the way from three large scutes on each side to one small one on one side. The tabula- tion below gives the number of the specimen, the sex, the length and breadth of carapace in millimeters, the occurrences of infra- marginals on the right and left sides separately. Three general sizes are distinguished, which although quite arbitrarily laid down may serve to give a more definite idea of the amount of variation that occurs. These sizes are designated as large, medium and small.
At Woods Hole this summer I found two specimens of Nan- ncinys gnttata and three specimens of Chrysemys picta with well marked inframarginals.
It will be readily seen that in both species the middle scute is much the commonest recurrence, and this is natural if we consider that in Chelydra, and other species with well developed infra- marginal rows, the middle scute is always the largest. The largest and most vigorous scute would probably persist longer and hence be most likely to recur as an atavistic reminiscence. The fact that no. III. is next in prevalence in Grapteuiys and no. I. in Chrysemyjs, indicates that the order of suppression of the other scutes of the row was subject to individual and group variation.
In the species Chelydra serpentina the inframarginal row is in a highly variable condition. Many stages in the reduction of numbers of scutes are to be seen in different individuals. The middle scute, corresponding to no. II., is always the largest, and the adjoining ones are next in size and would correspond to no. I. and no. III. Frequently there are two or three smaller scutes both in front of and behind the large central scutes, but
ABNORMALITIES IN CHELONIA.
79
GRAPTEMYS GEOGRAPHICA.
|
No. |
Sex. |
Length in Breadth in mm. mm. |
Right Side. |
Left Side. |
|
|
I |
F |
98 |
81 |
Small II. |
Medium II. |
|
2 |
F |
189 |
139 |
Small II. |
|
|
3 |
F 200 |
171 Small II. |
|||
|
Large III. |
|||||
|
4 |
M 109 |
82 |
Medium I. |
||
|
5 |
F 75 |
63 |
Large II. |
Medium II. |
|
|
6 |
63 57 |
Medium III. Medium III. |
|||
|
7 |
M |
82 70 |
Small II. |
||
|
8 |
? |
63 |
56 |
Large II. |
|
|
9 |
F |
75 |
63 |
Small III. |
|
|
10 |
? |
60 |
54 |
Small II. |
Medium II. |
|
ii |
? |
57 |
Large II. |
Large II. |
|
|
Large III. |
Large III. |
||||
|
12 |
F |
195 |
147 Large III. |
Large 11. |
|
|
Large III. |
|||||
|
13 |
F |
1 60 |
118 |
Medium III. |
Large III. |
|
14 |
F |
99 |
82 |
Medium I. |
Medium I. |
|
Medium II. |
Medium II. |
||||
|
Medium III. |
Medium III. |
||||
|
'5 |
F |
94 |
82 |
Large II. |
Large II. |
|
Large III. |
|||||
|
16 |
F |
134 |
112 |
Large I. |
Large I. |
|
Large II. |
Large II. |
||||
|
17 |
F |
101 |
76 |
Medium I. |
Large 11. ( See |
|
Fig. 44. ) |
|||||
|
Large II. |
Large III. |
||||
|
Large III. |
|||||
|
18 |
M 88 69 Medium I. |
||||
|
19 |
M 95 73 Large II. |
Large II. |
|||
|
Large III. |
|||||
|
20 |
? |
56 |
51 Small II. |
Small II. |
|
|
Small III. |
|||||
|
21 ? |
55 |
50 Medium II. |
Medium II. |
||
|
22 |
? |
57 |
53 |
Large II. |
Large II. |
|
23 |
? |
62 |
54 |
Large II. |
Large II. |
|
Large III. |
|||||
|
24 |
F |
So |
65 |
Medium II. |
|
|
25 |
M |
60 |
50 Large II. |
Medium I. |
|
|
Medium II. |
|||||
|
26 ? |
51 |
48 Medium II. |
Medium II. |
||
|
Medium III. |
|||||
|
27 |
? |
58 |
53 Small III. |
||
|
28 |
M |
66 |
54 Medium II. |
Medium I. |
|
|
29 |
• M |
1 10 78 Medium III. |
|||
|
30 M 97 77 |
Small II. |
they shown signs of suppression and in the majority of specimens are of insignificant size. The axillary and inguinal scutes of the Emydidae, etc., correspond, I believe, to two of these smaller scutes that are undergoing suppression in Chelydra. They have persisted in the Emydidae probably because they were needed to fill in the angles between the plastrals and marginals. Aroma-
So
H. H. NEWMAN.
CHRYSEMYS MARGINATA (188 specimens examined).
|
No |
Sex. |
Length in mm. |
Breadth in mm. |
Right Side. |
Left Side. |
|
I |
F |
IO4 |
80 |
Medium II. |
|
|
Medium III. |
|||||
|
2 |
F |
116 |
88 |
Small II. |
|
|
3 |
F |
IO2 |
81 |
Large I. |
|
|
Large II. |
Large II. |
||||
|
4 |
M |
85 |
67 |
Medium I. |
Small III. |
|
Medium II. |
|||||
|
5 |
F |
90 |
73 |
Small II. |
Small II. |
|
6 |
M |
96 |
72 |
Large I. |
|
|
7 |
F |
98 |
80 |
Large I. |
|
|
8 |
? |
55 |
50 |
Medium I. |
Large 11. |
|
Medium II. |
|||||
|
9 |
M |
72 |
58 |
Small II. |
Small II. |
|
10 |
F |
"3 |
86 |
Large II. |
Large II. (See Fig. 43 ) |
A tabulation of the above results shows :
Right Side. I. 4 scutes
II. 20 " III. 13 «
Total : 37 "
Right Side. I. 4 scutes II. 8 " III. I "
Total : 13 "
Grapheniys •
Ch rysemys
Left Side 5 scutes
20 " 10 "
35 "
Left Side. 2 scutes
4 " I "
chclys odorata (Fig. 53) shows a curious survival of inframarginals, having invariably only two scutes, one large and the other very small and vestigial. From its position, separating the pectoral shields from the marginals, I would homologize this large scute with no. II. and the vestigial scute with no. I. Complete sup- pression of the inframarginal row has occurred in the terrestrial genera of the Emydida?.
2. Interplastrals.
The occurrence of traces of the interplastral row are not nearly so frequently found as those of the inframarginals. Yet they are sufficiently numerous and definite to note in this con- nection. Traces have been found in Chelydra, Grapteuiys and Cliryseinys. In preparing a list of these occurrences it will be convenient to number the places where such scutes might occur,
"ABNORMALITIES" IN CHELONIA. 81
A,B, C, D and E, beginning at the anterior end. Two specimens of Chrysemys marginata have extra scutes at A (Fig. 47). Two specimens of Chclydra have extra scutes at C (Fig. 45). One specimen of Graptcuiys has extra scute at D (Fig. 48). One specimen of Graptcmys has a pair of extra scutes at E (Fig. 46). The primitive condition was probably one in which a scute was present at each point of union of four plastron scutes, but the fact that even in the tail of Chelydra this row is either partially or wholly wanting indicates the rather uncertain character of the row. In the specimens listed above scutes are found occur- ring in four places out of a possible five. No doubt a larger col- lection would serve to fill in this gap.
I consider these recurrences as true reversions to ancestral conditions ; and that they come under the head of systematic atavism I see no reason to doubt.
How the typical number of scute rows seen in our modern tortoises has been acquired has, perhaps, been sufficiently dis- cussed and it now seems necessary to consider the processes that have brought about the reduction of the number of scutes in a row — for it is beyond dispute that such a reduction has taken place.
3. Supernumerary Scutes in a Row on the Carapace.
The literature on this subject is limited to one paper, Gadow's much-discussed " Orthogenetic Variation in the Scutes of Che- Ionia," that was published in Willey's Zoological Results in 1899. The author gives a very interesting account of the con- ditions found in the common loggerhead turtle, Tlialassoclielys carctta. He has gathered together a miscellaneous assortment of some sixty-nine specimens of various sizes, principally new- born, from many parts of the world. On the basis of this col- lection he comes to the conclusion that scute reduction proceeds along certain definite lines. His observations, however, are limited to reductions in the neural and costal rows. According
t>
to Gadow, the ideal ancestral condition is one in which the neural and costal bony plates determine the number of scutes. The author's idea is that there was originally a scute for each of these plates.
82 H. H. NEWMAN.
Starting with this ideal condition as stage I., he finds the nearest approach to it in specimen I, that has 8 left costals of which 2 are vestigial, 8 right costals of which I is vestigial, and 8 neurals. The greatest reduction is that seen in specimen 26, which has 5 left costals of which I is vestigial, 4 right costals, and 7 neurals of which I is vestigial. This latter specimen is reduced below the normal for the species, which is arbitrarily said to possess 6 neurals and 5 pairs of costals. This condition is said to be the goal toward which every young Thalassochelys carctta is striving.
The following stages are mapped out in diagram, following Gadow, to show the sequence in scute reduction in the chelonian carapace :
Stage I. - - Hypothetical, eight neurals and eight pairs of costals. Neurals and costals lie in the same transverse plane and coincide with neurals and costal plates.
Stage II. - - Eight neurals and eight pairs of costals, the latter fitting with their inner angles dovetailed between two successive neurals. Rearrangement probably brought about by the partial reduction of one pair of costal scutes. This reduced pair is probably the second.
Stage III. - - Eight neurals and seven pairs of costals, the original second costals suppressed, original third becoming second, etc.
Stage TV. — Seven neurals and seven pairs of costals, but fifth neural and fourth pair of costals (original fifth), in a state of reduction.
Stage V. — Six neurals and six pairs of costals, owing to complete suppression of fifth neural and fourth (original fifth) pair of costals.
Stage VI. --Six neurals and five pairs of costals, brought about by fusion of last two pairs of costals into one or, perhaps, by suppression of one pair. This is the normal condition in Thalassochelys.
Stage VII. — Six neurals and four pairs of costals. Normal condition in the majority of tortoises to-day, brought about by suppression of first pair of costals.
Stage VIII. — Six neurals and four pairs of costals, first neural (nuchal) greatly reduced.
"ABNORMALITIES" IN CHELONIA. 83
Stage IX. — Five neurals and four pairs of costals, first neural (nuchal) suppressed as seen in pleuroderous tortoises.
Beyond this last stage chelonians have not ventured yet, at least normally.
The order of loss in scutes is according to Gadow : (i) No. 2 costals, (2) no. 7 neural, (3) no. 5 neural and no. 4 (original no. 5) costals, (4) no. 7 or 8 costals (by fusion or suppression), (5) no. i costals, (6) no. i neural.
Gadow's paper, while most suggestive, must be criticised in several particulars, but before proceeding to the criticism it will be necessary for me to produce the data that to a large extent form the basis of the criticism. The data are derived from a col- lection of a large number of abnormal specimens, principally of two species, Graptemys geographica and Chrysemys marginata. Gadow worked on a species that is normally abnormal — if such an expression be permissible. He selected the commonest con- dition and arbitrarily called it normal. As a matter of fact, there is no normal or fixed condition. The species TJialassochelys cwetta is evidently in a highly variable state as to scute number and arrangement, and no stability has as yet been attained. The species I have studied have, on the contrary, reached an advanced state of stability. Yet a sufficiently large number of abnormali- ties occur to give one nearly as many examples as Gadow had. Out of 476 specimens of Graptemys, varying from embryos to adults and taken at random, there occurred 48 specimens with supernumerary carapace scutes, while iSS CJirysemys yielded 8 such abnormal specimens. Four other species belonging to widely diverse groups yielded one abnormality apiece. It seems probable that abnormalities of exactly the kind that I have found so plentifully in the case of Graptemys and Cliryscmys are to be found in any species if enough specimens be examined.
In order to economize space in the tabulation of these abnor- malities brevity in the nomenclature of these vestigial scutes must be attained by numbering them. Combining Gadow's figures with my own results, I have good reason to believe that vestigial scutes occur between every two surviving normal scutes and that the first, second and last costals are also found in a vestigial con- dition. On this basis, then, there were eleven neurals and ten
84 H. H. NEWMAN.
pairs of costals. These, if numbered from anterior to posterior, would give the numbers I, 3, 5, 7, 9 and 1 1, to surviving neurals, and numbers 2, 4, 6, 8 and 10 to vestigial or lost neurals ; the numbers 3, 5, 7 and 9 to surviving costals, and numbers i, 2, 4, 6, 8 and 10 to vestigial or lost costals. In the tabulation these numbers will be used without further explanation. Furthermore, the sex, length and breadth of carapace, brief descriptions of both scutes and bony plates, will be given in separate columns. The significance of the tabulation of conditions of bony plates will be seen later when the subject of correlation between scute and plate abnormalities is discussed. The specimens are numbered and arranged in the order of abnormality, the specimens with largest number of extra scutes coming first, and those with less than the normal number of scutes last. Extra neurals will be listed be- fore extra costals and the latter before extra marginals.
Two kinds of abnormality may be distinguished : symmetrical and asymmetrical. The former are less common and are impor- tant in that they furnish clearer cases and thus throw light on the latter. Under the head of symmetrical abnormalities may be mentioned extra neurals in the median line or nearly so ; extra costals in pairs symmetrically placed ; extra paired marginals. The great majority of abnormalities are asymmetrical, consisting of: extra neurals crowded to one side or the other but usually showing clearly enough the position they would normally oc- cupy ; unpaired costals or marginals. In the case of asymmet- rical neurals it is sometimes difficult to distinguish the supernu- merary scute from the normal scute, on account of the large size of the former and the fact that crowding has forced the two scutes to lie approximately side by side. There are usually cor- related points of asymmetry that may be of assistance in deciding the point, but occasionally I have been compelled to trust to my judgment and may possibly have erred. Gadow would probably consider the type in which the normal and supernumerary scutes lie side by side as evidence of the original paired character of the neural row. Were it not for transitional conditions this view might be tenable.
Occasionally it becomes difficult to determine which of five costals is the supernumerary scute, but a reference to the mar-
ABNORMALITIES
IN CHELON1A.
GRAPTEMYS GEOGRAPHICA.
|
No. |
Fig. |
Sex. |
Length |
Breadth |
Scute Abnormalities |
Plate Abnormalities. |
|
in mm. |
in mm. |
|||||
|
I |
2O |
? |
60 |
54 |
Complete transverse |
Plates not fully |
|
row of 6 large scutes in formed. |
||||||
|
middle region. Difi&cult |
||||||
|
to diagnose. Double 6 |
||||||
|
neural (large). L 6 |
||||||
|
costal (large). R 4 cos- |
||||||
|
tal (large). Paired |
||||||
|
marginals. |
||||||
|
2 |
6 |
F |
188 |
144 |
Median 2 neural |
No. I procaudal |
|
(large). Paired i cos- |
fused with 8 neu- |
|||||
|
tals (large). Extra R |
ral. Extra R mar- |
|||||
|
marginal (large). |
ginal. |
|||||
|
3 |
35 |
? |
44 |
42 |
R 8 and 10 neurals |
Plates not fully |
|
(large). R 10 costal |
formed. |
|||||
|
( medium ) . L 10 costal |
||||||
|
(small). |
||||||
|
4 |
4 |
F |
122 |
97 |
3 neural partially di- |
R Marginal. |
|
vided. Probably indi- |
||||||
|
cates fusion of 3 and 4 |
||||||
|
neural. Paired I costals |
||||||
|
(large). R marginal |
, |
|||||
|
(large). |
||||||
|
5 |
5 |
F |
2OO |
H5 |
R 8 and 10 neurals |
9 neural. Dou- |
|
(large). R 8 costals |
ble extra procau- |
|||||
|
(large). |
dal. R costal |
|||||
|
( medium ). L |
||||||
|
costal (small). |
||||||
|
6 |
3 |
F |
189 |
139 |
R 10 neural (large). |
9 neural. Dou- |
|
R to costal (large). R |
ble extra procau- |
|||||
|
marginal (medium). |
dal. Paired 9 cos- |
|||||
|
tals (large). R |
||||||
|
marginal. |
||||||
|
7 |
13 |
M |
9S |
7i |
R 8 and 10 neurals |
Normal. |
|
(large). R 8 costal |
||||||
|
(large). |
||||||
|
8 |
H ' |
M |
84 |
70 |
L 10 neural (large). |
Normal. |
|
9 neural, partly divided, |
||||||
|
and probably represents |
||||||
|
8 and 9 neurals fused. |
||||||
|
L 10 costal (medium). |
||||||
|
9 9 |
F |
98 |
81 |
L 8 neural (large). |
Normal. |
|
|
10 and 1 1 neurals fused. |
||||||
|
L costal (medium). |
||||||
|
10 |
36 |
p |
52 |
47 |
R 8 and 10 neurals |
Bones not |
|
(large). Lacks a R |
formed. |
|||||
|
marginal. |
||||||
|
n |
34 |
(embryo) |
21 |
18 |
L 8 and -10 neurals |
B o.n e s not |
|
(large). formed. |
||||||
|
12 |
37 |
a |
25 |
21 |
R 10 neural (large). Bones not |
|
|
R 10 costal (medium), formed. |
||||||
|
13 |
8 |
Y |
174 |
136 |
R 10 neural (large). Extra procaudal. |
|
|
R ro costal (large). |
||||||
|
14 |
10 |
M |
U3 |
76 |
L 10 neural (medium ). \ Normal. |
|
|
L 10 costal (medium). |
||||||
|
15 12 M |
98 |
70 |
R lOneuralf .nedium). 9 neural. Paired |
|||
|
R 10 costal (medium). 9 costals. |
86
II. II. NEWMAN.
\ITEMYS GEOGKAI'HICA. — Coutillllt'i/.
|
No. |
Fig. |
Sex. |
Length |
Breadth |
Scute Abnormalities. |
Plate Abnormalities. |
|
in mm. |
in mm. |
|||||
|
16 |
40 |
? |
57 |
51 |
L 10 neural ( medium ) . |
Bones not |
|
I, 10 costal (medium). |
formed. |
|||||
|
17 |
Same as |
M |
87 |
73 |
L I o neural ( medium ) . |
Normal. |
|
10 |
L 10 costal (medium). |
|||||
|
1 8 |
7 |
F |
170 |
138 |
6 and 7 neurals par- |
Only p b o t o- |
|
tially fused. 9 and II |
graphic record re- |
|||||
|
neurals completely |
tained. |
|||||
|
fused. L 6 costal (me- |
||||||
|
dium). |
||||||
|
*9 |
56 |
(embryo) |
12 |
10 |
R 8 neural (large). |
Rirs very ab- |
|
R marginal. |
normal. |
|||||
|
20 |
17 |
M |
89 |
69 |
Paired lo costals |
Normal. |
|
(small). |
||||||
|
21 |
See 17 |
F |
160 118 |
Paired IO costals (me- |
Normal. |
|
|
dium). |
||||||
|
22 |
See 17 |
? |
61 |
54 |
Paired IO costals (me- |
Bones not |
|
dium). |
formed. |
|||||
|
23 |
See 17 |
F |
209 |
169 |
Paired lo costals (me- Normal. |
|
|
dium). |
||||||
|
24 |
26 |
? |
5i |
45 |
Paired I costal (me- Hones not |
|
|
dium). formed. |
||||||
|
25 |
38 (embryo) |
23 19 Median 8 neural Hones not |
||||
|
(large). formed. |
||||||
|
26 |
39 (embryo) |
19 16 |
L 8 neural (large). |
Bones not |
||
|
formed. |
||||||
|
27 |
23 |
F |
192 |
154 |
Median IO neural Normal. |
|
|
(medium). |
||||||
|
28 |
15 |
M |
83 |
67 |
L I o neural (medium). Normal. |
|
|
29 |
it |
M |
109 |
82 |
L 6 neural (large). Normal. |
|
|
30 |
22 |
M |
75 |
63 |
Paired extra marginals Paired extra |
|
|
(small). marginals (small). |
||||||
|
31 |
1 6 |
M |
78 |
67 |
R 10 costal (large). |
Normal. |
|
32 |
See 1 6 |
M |
82 |
70 |
R 10 costal (large). |
Normal. |
|
33 |
See 1 6 |
F |
72 |
62 |
R to costal (medium). |
Bones not |
|
formed. |
||||||
|
34 |
See 1 6 |
? |
52 |
47 |
R IO costal (medium). |
P> i) n e s not |
|
formed. |
||||||
|
35 |
See 1 6 |
i |
63 |
56 |
R IO costal (medium ). |
Bones not |
|
formed. |
||||||
|
36 |
21 |
F |
66 |
57 |
L IO costal (medium). |
1! o n e s not |
|
formed. |
||||||
|
37 |
See 21 |
? |
57 |
5i |
L lo costal (medium). |
Bones not |
|
1 formed. |
||||||
|
38 |
See 21 |
? |
29 |
26 |
L 10 costal (medium).1 Bones not |
|
|
formed. |
||||||
|
39 |
See 21 |
? |
60 |
54 |
L I o costal (medium). |
Bones not |
|
formed. |
||||||
|
40 |
See 21 |
F |
73 63 |
L IO costal (medium). |
Bones not |
|
|
formed. |
||||||
|
4i |
See 21 |
F |
99 82 L TO costal (small). |
Normal |
||
|
42 |
See 27 |
p |
47 42 L marginal lacking. |
Bones not |
||
|
formed. |
||||||
|
43 |
27 |
? |
58 52 L marginal lacking. Hones not |
|||
|
formed. |
||||||
|
44 |
19 |
F |
72 |
64 |
R marginal lacking. |
R marginal |
|
lacking. |
ABNORMALITIES IN CHFIONIA.
i ;K \rrrM\s CKUIKAI-IIICX.—
|
No. |
Fig. |
Sex. |
Length in nun. |
Krendth in nun. |
Seine Abnormalities. |
Plate Almormnlities |
|
4S |
See 19 |
? |
58 |
53 |
R marginal lacking. |
1 '. 11 n e s not |
|
formed. |
||||||
|
46 |
18 F |
77 65 |
Paired marginals luck- |
Paired marginals |
||
|
ing. |
lacking. |
|||||
|
47 |
( embryo) |
1'aircil marginals lack- ing and costals not fully |
Hones not formed. |
|||
|
1 |
differentiated. |
CllKVSK.MVS MARC1NATA.
|
No |
Fig. |
Sex. |
Length in nun. |
Breadth in mm. |
Scute Abnormalities. |
Plate Abnormalities |
|
4S |
31 |
F |
130 |
93 |
R 8 and IO costals |
Kxtra 1'iocau- |
|
(large). |
dals. |
|||||
|
R 10 costal (large). |
||||||
|
49 |
32 |
F |
73 |
61 I, 8 and 10 neurals |
Normal. |
|
|
(large). |
||||||
|
50 |
30 M |
104 So Paired IO costals |
Normal. |
|||
|
(large). |
||||||
|
51 |
25 52 47 Paired 4 costals (me- |
Bones not fully |
||||
|
dium ). |
formed. |
|||||
|
52 |
24 57 50 L 4 or R 6 neural. |
Hones not fully |
||||
|
formed. |
||||||
|
53 |
20 F 84 67 |
R 10 neural (large ). |
Normal. |
|||
|
54 |
28 M |
97 |
(,o |
L I costal (medium). |
Normal, |
|
|
55 |
41 F |
73 |
63 |
L 8 costal (medium). |
Normal. |
ginals will usually settle the point, as the normal condition has a very characteristic arrangement of these t\vo sets of elements.
Another source of difficulty arises from the complete or in- complete fusion of adjacent scutes. Fusion is due to the inhibi- tion of the process of division into epidermal areas at a rather late embryonic stage. In some cases the fused scutes show their separate identity, after a year or two of growth, by a separation of their growth rings. Coker has called attention to several such cases in connection with Malaclcunnys ccntrata and I have observed the same phenomenon in the marginals of Graptcinys on several occasions. Usually, however, the indications are clear enough to enable one to recognize the individual elements in a fused scute. It seems reasonable in the present discussion to consider the number of scute primordia involved in a fusion and to give them the full rank of independent scutes.
As in the previous tabulation, the arbitrary terms, large-, small and medium, are used. Lor R in connection with neurals will
88 H. H. NEWMAN.
indicate that the extra scute is crowded to left or right. The same letters indicate the side on which extra costals and mar- ginals occur.
The following isolated abnormalities have come to hand and may be listed :
Large specimen of Terrapene Carolina has a R 10 costal (medium).
Medium-sized shell of Cyclcmys doitata has paired 6 costals (medium). See Fig. 42.
Two medium-sized specimens of Chelydra scrpcntina have L 10 costal (large).
Large AronwcJielys odorata has R 10 costal (medium).
A reference to the literature enables me to list a considerable number of similiar abnormalities. The names used in the refer- ences will be retained.
1. Ptychemys clcgans, Agassiz, L., Contributions to the Nat- ural History of the U. S., Plate I, Fig. 13, showing: L 4 neu- ral, paired 4 costals, paired extra marginals. (Figured in this paper as Fig. 33.)
2. Chelopas insailptns, Parker, G. H., paired marginals lacking.
3. Same : R 8 and 10 neurals, R 10 costal, R marginals lacking.
IN CATALOG OF SHIELD REPTILES IN THE BRITISH MUSEUM.
4. Emysvermiculata^zb. XIII.), 24 neural, R 8 and 10 neural.
5. Emys singuinulenta (Tab. XV.), R 6 neural, R 6 costal, L 4, 6 and 10 costals.
6. .Cyclcmys dentata (Tab. XIX.), median 4 neural, R 6 neural, L 8 neural.
7. Chclodina oblonga (Tab. XXIV.), R 8 neural.
IN HISTORIA TESTUDINUM, SCHOEPFF, J. B., 1792.
8. Testudo cincra (Tab. III.), Fig. 2, paired I costals.
9. Tcstndo arcolata (Thunberg), Tab. XXIII., median 8 neural, L 6 costal.
10. Tcstndo planiccps, XXVII. , L 4 costal.
Discussion.
A scute, whether normal or supernumerary, is a separate and definite entity, resulting from a definite embryonic primordium.
ABNORMALITIES IN CHELON1A.
89
The fact that supernumerary scutes have been found between all of the normal scutes as well as at both ends of the costal series must have some significance. If one assumes that these super- numerary scutes represent the atavistic recurrence of scutes that have been lost in the course of phylogeny, it is possible that the following tabulation will throw some light on the sequence of loss.
|
Neural 's. |
Costah. |
||
|
No. of Scute. |
Numbers of Recurrences. |
No of Scute. |
Numbers of Recurrences |
|
2 |
I |
I |
6 |
|
4 6 8 10 |
2 (one doubtful) 5 (one doubtful ) II (one doubtful) 1 6 (one doubtful) |
2 4 6 8 |
o 3 4 (one doubtful) 4 (one doubtful) |
|
10 |
35 |
It will be seen that the most frequent recurrences are at the posterior end of the carapace, and that, with the exception of the first costal, the frequency of recurrence diminishes as we proceed anteriorly. What significance attaches to this fact ? It seems quite probable that the most frequent recurrences represent the most recent losses and the rarest recurrences the most ancient losses. This rule held good for the suppression of rows of scutes and should apply here also.
On this basis then we can at least say that the succession of suppression was in general antero-posterior, that the earliest losses occurred at the anterior end of the carapace and the most recent losses at the posterior end. One might go further and say that in the neural series the order of suppression was probably 2, 4, 6, 8 and 10. The antero-posterior order of loss is not so clear in the case of the costals, as no. I costal recurs more fre- quently than any other except no. 10. This means a modifica- tion of the regular mode of progression. In the costal series it is probable that the antero-posterior succession of losses was interfered with by the rounding-in of the marginals both ante- riorly and posteriorly. This rounding-in would necessarily begin about medially and proceed in two directions, hence the second supernumerary scute would be put under pressure before the first and the eighth before the tenth. The antero-posterior
H. H. NEWMAN.
tendency, however, would bring about the suppression of anterior scutes, as a whole, before posterior scutes.
Evidences are not wanting that scutes may be suppressed and the method of suppression seems clear. In a specimen of Cycle- mys dentata, listed as no. 58 and figured on Plate III., Fig. 42, the paired sixth costals are being encroached upon by the seventh costals. The anterior growing margins of the latter have pushed in under the posterior edges of the former in such a way as to severely cut into their growth centers. The dotted line shows the amount of encroachment. Several specimens of Graptemys show the same phenomena, and the scutes encroached upon are always the supernumerary ones. This may be looked upon as a recurrence of an ancestral condition and we may infer that the loss of certain scutes has been brought about through the encroachment, more and more severe with succeeding genera- tions, of more vigorous upon less vigorous scutes, resulting in the final complete suppression of the latter. We must also suppose that the rudiments of the lost scutes lie dormant in the embryonic tissues and occasionally for some reason reappear more or less completely. Those that have been suppressed for the longest time would naturally reappear least often and vice versa. On this basis, then, we may safely say that the order of loss is orthogenetic if by this we simply mean onward develop- ment.
Applying the same methods to Gadow's figures I find a very general agreement, although 1 am unable to agree with the author's interpretations. The vestigial scutes that occur in Gadow's figures are : neurals 2, 8 and 10; costals I, 2, 4, 6, 8 and 10. No. 2 costal was not found in my specimens, but is so clearly seen in Gadow's Fig. I that I have introduced it into my system. It is possible that No. 2 costal was the most ancient loss and hardly likely to recur in specialized types such as Graptemys and C/iiysernys, since it occurred only once in Gadow's specimens of TJialassoclielys. It will be seen that Gadow finds no vestiges of neurals 4 and 6. An examination of his figures will show that TJialassochclys has attained a high degree of fixity in the anterior portions of the mid-neural series, while all other regions are still in a decidedly variable condition. Hence we are
"ABNORMALITIES IN CHELONIA. 91
unlikely to find vestigial scutes in this region unless a much larger number of specimens is examined.
Carapace abnormalities have been pictured by authors for over a century and I have on my lists fourteen species, belonging to widely diverse groups, that show the same general abnormalities.
These scattering cases could scarcely be used in determining the order of loss of scutes, but are of importance in that they show that certain abnormalities that are comparatively rare in Graptemys and CJiryseitiys occur with a fair degree of frequency in other forms. For example: neurals 4 and 6, and costals i, 4 and 6 occur from 2 to 4 times in these specimens. The prev- alence of abnormalities of this sort over such a wide range of forms strengthens my idea of the universality of the process of scute reduction in Chclonia. I have no doubt that such ab- normalities will be found in any species if enough forms are examined.
In Gadow's diagrams illustrating the progressive reduction of epidermal scutes (p. 217) it will be seen that the order of reduc- tion differs from the one I have proposed in two points ; in the first place he indicates that no. 10 neural is suppressed before no. 8, but this is not borne out by his own figures. Figs. 4, 6, 7, 14, 20, 26, show no. 10 persisting after the total suppression of no. 8, Fig. 26 being especially convincing. Figs. 8, 9, 10, on the other hand, show no. 8 persisting after the suppression of no. 10. The balance is decidedly in favor of the earlier sup- pression of no. 8, yet there must have been some individual vari- ation in this matter. My own figures show that no. 8 recurs twelve times as compared with seventeen times for no. 10. In my own specimens there are eight cases in which nos. 8 and 10 neurals recur together, nine cases of no. 10 recurring alone, and only four of no. 8 recurring alone. It would seem then that these two scutes were undergoing a process of suppression at about the same time, but that no. 8 was in most cases the first to disappear.
In the second place it seems clear that no. I costal persisted longer than no. 10 in Thalassochelys, but that the opposite was the case in all the forms in my collection can scarcely be doubted, no. 10 recurs thirty-six times and in many species, while no. i recurs only six times.
92 H. H. NEWMAN.
Some rather remarkable conclusions are expressed in Gadow's paper and should be discussed in this place.
1. He makes the following statement : "Abnormalities are 4 to 7 times as common in new-born as in mature specimens, hence scute reduction must take place during the lifetime of the indi- vidual." I have not had the opportunity of putting this matter to a test in the case of TJialassoclielys, but the examination of several complete nests of Graptemys has brought to light the following facts. Two nests containing respectively thirteen and fourteen embryos showed no abnormalities. One nest contain- ing fourteen just-hatched young showed one slight abnormality, a vestigial no. 10 costal. A fourth nest in which twelve eggs came to maturity contained five decidedly abnormal specimens, listed as nos. 11, 19, 25, 26 and 48. This means that barely 10 per cent, of the embryos of four broods are abnormal, while out of 476 specimens of Graptemys 48 were abnormal in the carapace scutes, a little over 10 per cent. A large proportion of Gadow's new-born specimens came from one nest, the whole brood of which was abnormal. The others were taken in small sets from various collections, and I believe that such specimens had been preserved because of their abnormalities. A survey of my tabulations will show that abnormalities are no more common in one size than in another. Finally, Coker, in a very recent preliminary paper, delivered before the American Society of Zool- ogists in Philadelphia, December, 1904, claims that observations on embryos of TJialassochelys gave no support to the theory of Gadow.
2. Gadow considers that certain specimens (Figs. 6 and 24) show evidences that the neural row was originally a double one. That this was the case seems very unlikely from an examination of such primitive conditions as are seen in the tail of CJielydra and in the neural keel of DermocJielys. The appearances seen in Figs. 6 and 24 may be due to the crowding of linear members of the row until they come to lie side by side. Indications of an approximation to this condition are not uncommon in the speci- mens which I have had to deal with.
"ABNORMALITIES IN CHELONIA. 93
4. Supernumerary Scutes on tlie Plastron.
The plastron has, as a rule, reached a higher degree of fixity in the matter of numbers and arrangement of scutes than has the carapace, but that this portion of the chelonian armor has not al- ways had so fixed a character may be seen in the high state of variability of Aromochclys odorata, which is almost as marked as that seen on the carapace of Thalassochelys. In Aromochclys the number of plastron scutes varies from 14 to 9 and all intermediate conditions are readily found. Fig. 5 2 shows the largest number of scutes seen in the specimens of my collection. In this case there is a well-developed extra pair of scutes between the abdominals and femorals. Fig. 53 shows the commonest condition in which there are the usual five pairs of plates and the gulars are par- tially fused. Fig. 54 shows the extreme of reduction in which the pectorals have been lost either through crowding or fusion, and the gulars have fused into a single median element.
As in the case of the carapace, we find in several species that have attained a high degree of fixity in the plastron, marked traces of supernumerary scutes. Fig. 49 shows the plastron of a small specimen of Chelydra that has an extra pair of scutes be- tween femorals and anals. Fig. 50 shows another specimen of Chelydra with a vestigial scute on the right side between humeral and abdominal. Fig. 51 shows a specimen of CJirysemys with a well-marked supernumerary scute on the left side between ab- dominal and femoral. In Figs. 49, 50, 51 and 52 we have super- numerary scutes in four places out of a possible five. As yet I have been unable to find supernumerary scutes between gulars and numerals.
Losses seem to have taken place in two ways : by fusion and by crowding out. Some curious examples of the latter might be mentioned. In Chelydra the abdominals have been forced to the sides, but have been retained to bridge the gap between the small plastron and the margin of the much larger carapace. In other cases the pectorals have played a similar role. Van Lidth de Jeude describes a specimen of Tcstudo ephippium (Gthr.), in which the pectorals have been crowded to the two sides lika the abdominals of Chelydra. Other specimens of the same species, according to Rothschild, have the same abnormality to a greater
94 H. H. NEWMAN.
or less degree. The Catalogue of Shield Reptiles in the British Museum shows a specimen of Mononria fnsca (Tab. III.), in which the pectorals are crowded to the margin of the plastron and have become small and triangular. The same volume shows a specimen of Sternotherus Derbianns (Tab. XXII.), in which the pectorals seem to have a tendency to be suppressed or crowded to one side.
On the whole it seems evident that an orderly suppression of alternate scutes has taken place in the plastron as well as in the carapace.
5. Correlated Abnormalities in tJie Scutes and Bony Plates.
The next question that comes up for discussion is whether or not there is any correlation between scutes and bony plates. It has long been noticed by morphologists that there is a certain definiteness about the relative positions and sizes of scutes and plates. This may be described in brief as a definite overlapping of bony sutures by scutes. In the marginal series (see Fig. i) this is seen in its simplest form — every bony suture being covered by a scute. In the neural and costal series one scute as a rule covers one whole plate and half of two adjoining plates. This arrangement is modified in the anterior and posterior regions. In the former the nuchal plate is partially overlapped by six scutes, viz. : nuchal, first pair of marginals, first pair of costals (normally involving only small corners of the plate), and the first neural. The first costal scutes cover the first and half of the second cos- tal plates as well as the inner edges of first, second, third and fourth marginal plates. The last neural covers normally parts of eight plates, viz. : the two procaudals and the anterior margin of the pygal, about half of the eighth neural and eighth pair of costals, and the anterior margins of the eleventh marginals. Only in the middle portions of the carapace is any definiteness of arrangement seen, yet there is a marked fixity of relations even in the most specialized regions. Gadow bases his reduction series upon an arbitrary connection between these structures, according to which there was originally a scute for each vertebra and rib. He gives no reason for assuming a vital connection between these structures, but simply implies one. In an earlier portion of the
"ABNORMALITIES IN CHELONIA. 95
present paper it has been shown that there is no ontogenetic con- nection between the scutes and plates, the former being laid down before the latter have begun to form, while the latter appear com- paratively late in development as mere outgrowths of the ribs and neural spines.
If, however, there be any essential connection between these scutes and plates, we would expect to find scute irregularities and abnormalities associated with plate irregularities and abnormalties and vice versa.
G. H. Parker ('99) expresses himself at some length on this point in a paper entitied " Correlated Abnormalities in the Scutes and Bony Plates of the Sculptured Tortoise." He describes in detail two abnormal specimens and on this slender basis reaches some rather general conclusions.
Specimen no. i has extra eighth and tenth neurals and a small right tenth costal. No plate abnormalities are found in the neu- rals or costals, but one right marginal plate and a correspond- ing scute are lacking. Parker designates these conditions as : (a) Scute abnormalities unassociated with plate abnormalities, ($) scute abnormalities associated with plate abnormalities.
Specimen no. 2 has normal neural and costal scutes, but lacks an entire horizontal row of plates consisting of a neural, a pair of costals and a pair of marginals. The lack of marginal plates is associated with the lack of a corresponding pair of scutes. These