Gestation in Batrachians and Fishes, 45 



there is a vitelline placenta analogous to the Allantoidian one of 

 the Mammalia.* 



To those species enumerated above where the eggs become 

 more or less intimately connected with the body of the parent 

 after they are laid may be added the Aspredos and some species 

 of Bagrus, from Guiana. 



Aspredo Icevis (Cuv. and Val.), the "Trompetti" of the colonists, 

 is about fifteen inches in length, and belongs to a remarkable ge- 

 nus of Siluroid fishes, which, in addition to several peculiarities 

 of anatomical structure, are remarkable for carrying the eggs and 

 young attached to the under surface of the body. These fishes 

 are very abundant in the waters of the Surinam where they are 

 taken in the nets with other kinds. They are not used as articles 

 of food except by the negroes, who have a fancy for Siluroids 

 generally, and in consequence these are known among the colo- 

 nists as Ningrefisi or "nigger fish." A general account of the 

 internal structure of Aspredo, is given in the Hist. Nat. des Pois- 

 sons, by Cuvier and Valenciennes, t. xv, p. 35. 



In the month of June the eggs are found adhering to the un- 

 derside of the body, to the ventral and pectoral fins, and extend 

 as far forward as the under lip, and as far backwards as the mid- 

 dle of the tail. In some however the distribution is much more 

 limited. I was unable to learn anything with regard to the transfer 

 of the ova from the genital orifice to the point of their attachment. 

 The only organ which seems in any way adapted to such a purpose 

 is the slender and flexible tail terminated by a delicate caudal fin. 

 It is possible that the eggs may be deposited on the bottom of the 

 river, and subsequently attached by pressing the underside of the 

 body upon them. 



In those individuals where the ova were still in the ovary, but 

 approaching maturity, the integuments of the underside of the 



* Prof. Owen (in Philos. Transactions, 1834,) has pointed out the vas- 

 cular relations of the foetal Kangaroo to the parent. The chorion is not 

 rascular, but the umbilical vesicle is largely provided with blood ves- 

 sels, and, as far as his investigations go, affords the principal vascular 

 surface by means of which an interchange takes place between the foetus 

 and the parent. The vitelline circulation then, as in sharks, is the res- 

 piratory circulation. The allantois of the Marsupials appears to remain 

 in a rudimentary condition, and does not form a connection with the 

 parent. Thus the vascular relation of the foetus of some of the sharks, 

 as Carcharias, with the parent is identical with that of the Marsupials. 



