H4 CHIM^ROID FISHES AND THEIR DEVELOPMENT. 



preserved specimen of this species one which was examined in the Copenhagen 

 collection the colors had notably changed. The pigmented margins of caudal 

 and postdorsal fins had become reduced to a dusky band, and the marking of the 

 pectoral was limited to a mere fuscous blotch at the fin tip (fig. 92). The length of 

 this specimen was but about two inches greater than the former one. 



From the foregoing notes we may justly conclude that Chimaera undergoes 

 a series of "larval" changes. That these are adaptive remains still to be proven, 

 a verdict which, it may be remarked, applies equally well to many if not all the 

 "larval " changes of teleosts, but the fact that such changes do occur in the hatched 

 young is noteworthy in its bearing on the specialized nature of Chimaeroid 

 development. It is also, I believe, significant that the "larval " coloration of the 

 young of Chimtzra monstrosa occurs at an earlier relative period than in C. colliei 

 (i. e., that the distinctness of coloration, which in C. colliei a smaller species by the 

 way is shown in a specimen twelve inches in length, is attained in monstrosa by 

 the time the young measures but about seven inches), for this denotes that the 

 structures of monstrosa are the more highly differentiated and that this species is 

 of later origin. In another direction it contributes testimony as to the abbrevia- 

 tion of developmental processes. 



ORGANOGENY. 

 INTEGUMENT AND DENTITION. 



In the major problem of the position of Chimaeroids the evidence of scales and 

 dentition claims an important place. For the question has been raised repeatedly 

 whether the dentition of these fishes is fundamentally different from that of sharks, 

 and whether the characteristic tritoral plates may not have retained primitive gnath- 

 ostomal characters (Jaekel). And it has similarly been queried (Pollard) whether 

 the present integumental defenses of Chimaeroids may not prove the rudiments of 

 a complete body armoring. We may accordingly review at this point the evidence 

 in the matter of integument and teeth afforded by a study of the recent forms, both 

 in adult and in embryonic condition. 



It has long been known that recent Chimaeroids retain shagreen-like structures. 

 These occur in greater or less number (a) on either side of the median dorsal line ; 

 (<$) in connection with sensory canals, especially in the suborbital region; and (c) in 

 the male as organs of retention in copulo. 



(a) Shagreen-like scales on either side of the median line are most numerous in 

 Callorhynchus, where they form rows, each including about a dozen scales, in three 

 definite tracts, i. e., in the head, between the first and second dorsals, and between 

 the second dorsal and the caudal fin (figs. 93 A and B). In Harriotta they are 

 smaller and less numerous. In Rhinochimaera they are tumid and uncalcified, 

 occurring along the fleshy anterior margin of the caudal fin, obsolescent elsewhere. 

 In Chimaera they are rudimentary or absent. These scales occur, therefore, in a 

 regressive series, at one end of which stands Callorhynchus, at the other Chimaera; 

 and it is significant, I believe, that a condition closely similar to Callorhynchus 

 occurs in sharks, e. g., Pristiurus and Scyllium, as figured by Paul Meyer, who, 



