160 FISHES. 



individuals produce a greater number of ova than smaller 

 ones of the same species. The larger the size of the ova is 

 in a species, the smaller is the number produced during one 

 season. The ova of the Eel are almost microscopic. The 

 small sized roe in the Herring, Lump-fish, Halibut, and 

 Cod-fish, have been estimated at respectively 25,000, 155,000, 

 3,500,000, and 9,344,000. Larger in size and fewer in num- 

 ber are those of Antennarius, Salmo, Aspredo, Lophobranchs, 

 etc. Comparatively largest are those of Gastrosteus ; and 

 the Siluroid genus Arius, the males of which 

 take care of their progeny, produces ova from 

 5 to 10 millimeters in diameter. The ova of 

 Pi„ 71 all Teleosteans are perfectly globular and soft- 

 Ovum of Arius shelled. Teleosteans without oviduct, deposit 

 /"V showing them separated from one another ; whilst in many 

 embryo. Nat. Teleosteans with an oviduct the ova are en- 

 ^^^^' veloped in a glutinous substance, secreted by its 



glands, swelling in the water and forming lumps or cords, in 

 which the ova are aggregated. 



Instances of the female taking care of her progeny are 

 extremely scarce in fishes. At present only two examples 

 are known, that of the Siluroid genus Aspj^edo, and of Soleno- 

 stoma. In the former, during the time of propagation, the 

 integuments of the lower side of the flat trunk of the female 

 assume a soft and spongy texture. After having deposited 

 the eggs, the female attaches them to, and presses them 

 into, the spongy integument, by merely lying over them. 

 She carries them on her belly, as the Surinam Toad {Fipa) 

 carries her ova on the back. When the eggs are hatched the 

 excrescence on the skin disappears, and the abdomen becomes 

 as smooth as before. In Solenostoma the inner side of the long 

 and broad ventral fins coalesces with the integuments of the 

 body, a large pouch being formed for the reception of the eggs. 

 There is a peculiar provision for the retention of the eggs 



