December 30, 1892. J 



SCIENCE. 



367 



not so largely spotted as the one used in making the figure. 

 This absence of bilateral symmetry in the skin markings is 

 a more or less general phenomenon in the coloration of animals; 

 they rarely having their two siiles perfect counterparts. It is 

 in fact a case of a general law, applying to all bilateral organs, 

 perfect bilateraling being a very rare phenomenon, due, on 

 modern biological views, to the preponderance of growth in the 

 cells of one organ over its homologue of the opposite side through 

 the operation of any of the several causes which influence vitality 



of cells, e g., use, nutrition, di-ease. perhaps inheritance. But, 

 in animal coloration, while perfect bilatei-aling of marking is un- 

 usual, and a certain independence of the opposite sides is usual, 

 it is rarely carried so far as here. The markings of bu-ds. etc., 

 blend across the middle line, so, too, the blotches of snakes, frogs, 

 and other familiar cases, and I have never seen an animal in 

 which the independence of the color markings of the two sides is 

 as pronounced as it is in this form. A fact of this kind would 

 appear to have some important suggestions in relation to the 

 ontogenetic history of the yellow color producing cells. If they 

 are separated early in their history and continue distinct, we 



should expect such asepaiationin theirultimate product". There 

 are facts enoUf;h to indicate that in lower forms, such as annelids, the 

 cells of the two sides of the body in many of the organ systems are 

 separate f roil an early date, even as early as in the early segmentative 

 stage of the egg (cf., E. B. Wilson, '• The Cell Lineage of Nirus,"' 

 Journal of Morphology, vol, vi., p. 36, 1892). This supposition 

 would not be out of accord with the fact that the independence 

 of coloration is found in a lower rather than one of the higher 

 animal groups and in a lower member of its group for it is the 

 characteristic of the higher forms to have more and more inti- 

 mate relation of parts. The distribution of the color-spots I 

 cannot as yet reduce to any law by study of adults, and I know 

 of no observations in the embryology of Amblystoraa which 

 have been directed upon this point. There seem to be some faint 

 suffgestions of metamerism in the coloration of the area of the 

 side walls of the body, especially between the limbs. The body 

 wall in this region is marked on the ventral aspect and laterally 

 by rings (Myotirms), which correspond with the attachments of 

 the muscle fibres and the color spots are rather noticeably located 

 upon the rings rather than on the spaces between them. The 

 rings look like somites of an annelid, and it would be interesting 

 to know if they correspond with the segmentation of the vertebrae 

 and nervous system. 



2. The movements and locomotion of the salamander are very 

 inti^resting to observe. They suggest an animal which is passing 

 from the use of the hack-bone and its curvatures as a mechanism 

 for locomotion to the use of limbs. The locomotive movements 

 are of two classes, the first are those performed under ordinary 

 circumstances, the second those performed to escape from a pur- 

 suer as when one attempts to seize the creature The former are 

 made by means of a combined use ot the back- bone, which is 

 thrown into gentle curvatures, and the legs, which are the chief 

 insti'uments in the act. The curvature of the back-bone is such 

 as to throw the limb to be used forward further than it would be 

 with the spine kept straight. The limbs are used in strict alterna- 

 tion, the right front leg and the left hind leg going forward to- 

 gether, and then backward together, while the spine has a con- 

 vexity toward the right in the brachial region and toward the 

 left m the sacral region. The creature, in water, when disturbed 

 by one's hand gen'-rally either makes a disorderly scramble with 

 the limbs, which has but little result, or it swims swiftly with a 

 truly fish-like sinuation of the body, including the large post-anal 

 region or "tail," which is much compressed and forms a very 

 efficient organ of swimming. Tt has seemed to me that this 

 swimming motion may be a case of physiological reversion. We 

 know that the vertebral musculature is far more ancient phylo- 

 genetically than the limb musculature, and we may suppose that 

 hence the power to control it nervously is far greater than that 

 to control the more recently acquired limb musculature. It is a 

 case of the tendency to fall back on the ancestral mode of action 

 so long as the structure will permit, especially under circum- 

 stances in which the animal is under the influence of strong ex- 

 citement, which would tend to weaken the more recently acquired 

 powers and allow the ancient lines of habit to become dominant. 

 This tendency can be discerned in many other cases; thus, for in- 

 stance, I regard the case of the crayfish as precisely similar to the 

 one just cited. It commonly moves by a walking motion, not 

 using the flexion of the abdomen, but under excitement of escape 

 it reverts to this ancestral action, and the familiar "crawfish" 

 movement results. I do not think it is at all beyond the range of 

 reason to include the tendency of people to lapse into a native 

 language from an acquired one in moments of excitement under 

 the same principle of physiological reversion. In this connection, 

 I may speak of a specimen of Necturus, which I had for some 

 time in an aquarium in the laboratory, in which the swimming 

 movements were even more noticeable than in the salamander, a 

 fact co-ordinated with its more piscine peculiarities in other re- 

 spects. 



It is possible to discover in the movements a suggestion of the 

 origin of limbs. The limbs are usually in a line, and the front 

 right leg is thrown forward by the curvature of the body at the 

 same time that the left hind leg is thrown forward by the curva- 

 ture in its level. Limbs at these points, if at first mere stumps. 



