1906.] ANATOMY OF THE OPHIDIA. 15 



authors, in their classical ' Ei-petologie Generale,' vol. vi. 1844, 

 remark, in a general sketch of the Pythons and Boas, upon the 

 investigations of Mayer on the rudimentary hind limb, but 

 say nothing as to sexual differences in form of the " ergots," i. e., 

 claws in which these limbs terminate. Later on they write of 

 Eunectes murinus (p. 531) : — " Ergots coniques, courts, recourbes 

 et pointus," stating also that they are " d'une tres petite dimension 

 chez des femelles ayant plus d'un metre de long." In Boa again 

 (p. 503) it is said that these claws are present, but " neanmoins 

 plus developpes chez les males chez les femelles." The inference 

 from these observations would surely be that while sexual differ- 

 ences exist between individuals in respect of those claws, they are 

 merely a matter of varying magnitude. It was possibly for this 

 reason that text-books, at least those which I have referred to, 

 have not noticed the matter. In the adult male Eunectes notretts 

 there is a very conspicuous pair of claws, which are sharply pointed, 

 compressed, and curved, the lower surface being ridged. In the 

 adu.lt female there is not a claw at all, but a bluntly conical 

 straight process, quite unlike the claw of the male. In both cases, 

 however, this terminal process is ensheathed in two bract-like 

 scales. In the young individuals the differences are as well 

 marked as in the adult. 



The mental groove in the young Anacondas differs from that of 

 the adult male. In both adults the mental groove was bordered by 

 five scales on each side. The two individuals, a male and a female, 

 appeared to be identical in the disposition of these scales. 



In the two youngest individuals, which died immediately on 

 birth, the conditions were as follows : — In one snake, on the right 

 side the mental groove was bordered by only three scales ; but 

 the middle one was verj^ large, and indentations appeared to show 

 that it was in reality composed of three. On the left side there 

 were only four scales bordering the mental groove, but the 

 anterior one of these was partly divided into two ; thus the total 

 on both sides is really five as in the adult. The second specimen 

 was identical on the right side, but on the left the second scale, 

 and not the first, was obviously composed of two. In the young- 

 Anaconda which lived for three weeks* there is a still closer 

 approximation to the conditions observable in the adult. On the 

 left side of the mental groove all five scales are separated ; on 

 the right there were four scales, the second being much the largest 

 and obviously representing two. 



Kidneys. — The kidneys of these young Etcnectes have a form 

 which is remarkable. It is illusti-ated in the accompanying figure 

 (text-fig. 4, p. 17). The part of the kidney which appai'ently corre- 

 sponds to the whole kidney of other Snakes has the usual form 

 which is characteristic of Serpents and needs no particular remark. 

 The kidney does not, however, end off in front without much 

 diminution of diameter. It suddenly narrows to form a slender 



* This specimen shed its skin at any rate once, which doubtless accounts for the 

 change, not therefore referable to individual variation. 



