COO ANATOMY OF VERTEBRATES. 



in the male viviparous Blenny, which, by eversion of the 

 terminations of the sperm-canals, impregnates internally. The 

 claspers in the male Plagiostomes then acquire their full deve- 

 lopement and force: the basal glands in those of the Kays 

 enlarge. In Osseous Fishes the whole abdomen swells, and the 

 viscera are displaced by the prodigious bulk of the germinal and 

 seminal matter. 



As the period of ' fecundation ' approaches, the female osseous 

 fish seeks a favourable situation for depositing her spawn, usually 

 in shoal water, where it can be most influenced by solar warmth 

 and light. The marine Herring, Mackerel, and Pilchard approach 

 the shore in shoals : the fluviatile Salmon quits the estuary to 

 ascend the river, overcoming, with astonishing perseverance and 

 force, the rapids or other mechanical difficulties x that impede its 

 migration to the shallow sources, whither the sexual instinct 

 impels it as the fit place for oviposition. The female fish is 

 closely pursued by the male, sometimes by two : in the Capelin 

 (Mallotus) these swim on each side of her, aiding by their 

 pressure in the expulsion of the spawn, and at the same time 

 impregnating it by diffusing over it the fluid of the milt : thus 

 absorbed in the sexual passion, they have been seen, on the 

 shores of Newfoundland, to rush on land in their spasmodic 

 course over the shallows, which they strew with the fecundated 

 ova. In some genera violent combats take place between the males. 

 Mr. Shaw, 2 a close observer of the habits and developement of 

 the Salmon, states: — « On January 10, 1836, I observed a female 

 Salmon of about 16 lbs., and two males of at least 25 lbs., engaged 

 in depositing their spawn. The two males kept up an incessant 

 conflict during the whole day for possession of the female, and, 

 in the course of their struggles, frequently drove each other 

 almost ashore, and were repeatedly on the surface, displaying 

 their dorsal fins and lashing the water with their tails. The 

 female throws herself at intervals of a few minutes upon her side, 

 and, while in that position, by the rapid action of her tail, she 

 digs a receptacle for her ova, a portion of which she deposits, 

 and, again turning upon her side, she covers it up by the renewed 

 action of the tail, thus alternately digging, depositing, and covering 

 the ova, until the process is completed by the laying of the whole 

 mass, an operation which generally occupies three or four days.' 



In the ovo-viviparous Osseous Fishes the well-developed cloaca! 

 papilla, in which the sperm-ducts terminate, doubtless serves to 



1 Save those erected by stupid cupidity to effectually bar the salmon's progress. 



2 cxxiv. p. 551. 





