FISHES. 355 



His observations leave little room to doubt that the ani- 

 mals in question are hermaphrodites ; without, however, 

 determining at what precise period, or in what position, the 

 eggs are impregnated. 



Although the sexual organs of fishes had been long 

 known, it was not until the middle of the 18th century 

 that any experiments were performed to ascertain the effect 

 of their abstraction. TULLY appears to have been the 

 first person who performed the operation, and an account 

 of his experiments has been published in the Gent. Mag. 

 vol. xxv. p. 416, and in Phil. Trans, vol. xlviii. p. 870. 

 When the abdomen of the fish is laid open, the milt or 

 roe carefully removed, and the wound sewed up again, 

 the fish appears to experience but little pain, and the wound 

 heals in a few weeks. These experiments have frequently 

 been performed on the carp, and they are attended with 

 little risk. The fish grows to a large size, and its flesh is 

 said to have a more delicate flavour. But castration has 

 never come into general use among the proprietors of fish 

 ponds, being seldom performed but from motives of curio- 

 sity or science. 



We have already stated, that the impregnation of the 

 egg takes place, in many species, after exclusion, and 

 the experiments which have been conducted to establish 

 this point, have likewise made us acquainted with the exis- 

 tence of hybrid Jishes. Even in a common fish pond, where 

 carp and trout are permitted to live in company, the carp 

 sometimes impregnates the eggs of the. trout, or the trout 

 those of the carp. The limits, however, within which this 

 irregularity is confined, have never been investigated with 

 care. 



Fishes exhibit very remarkable differences in regard to 

 the number of eggs which they produce. The rays and 

 sharks seem to prepare but a very limited number. RON- 



