PISCES FISHES. 



538 



ovaria of the female, and the kidneys and ureters, were accurately 

 described by Hunter, in the Catalogue 

 of his Collection, and their form and 

 structure are illustrated by the pre- 

 parations and drawings still preserved 

 in the College of Surgeons ;* but in 

 such fishes the testis of the male so 

 exactly resembles the female ovary, 

 that it was even imagined by Sir E. 

 Home that no males existed, or that 

 the females were themselves herma- 

 phrodite : according to Rathke,*f* how- 

 ever, the testes of the male are com- 

 posed of solid granules precisely like 

 the female ova ; and the secretion de- 

 rived from them is in like manner al- 

 lowed to escape into the abdomen, 

 from which it is expelled through si- 

 milar openings in the peritoneum. 



(581.) In the Sharks and Rays 

 we meet with a very important addi- 

 tion to the female sexual apparatus, 

 namely, an oviduct, by which the germ 

 is seized on its escape from the ova- 

 rium, and furnished . with additional 

 coverings necessary in such fishes for 

 the security of the fetus. 



In these genera the folds of the 

 ovarian membrane become less exten- 

 sively spread out; and, from the size of the yolks of the eggs 

 formed therein, the organ assumes a racemose appearance. The 

 ovaries now form two large bunches placed on each side of the 

 spine; and the ova when mature would necessarily escape into the 

 abdominal cavity, as those of the Lamprey and Eel do, were they 

 not seized by the patulous orifices of the two long and membranous 

 oviducts whereby they are conveyed out of the body. 



(582.) There is, moreover, in the CHONDROPTERYGIOUS 

 FISHES a necessity for defending the young during the earlier 

 stages of their growth, by means which it would have been quite 

 foreign to the purposes of Nature to have adopted in the other 



* See Physiol. Catalogue, vol. iv. pp. 48. 129, pi. 59 and 60. 



t Neueste Schriften der Naturforschenden Gesellschaft zu Danzig. Halle, 1824. 



