FISH-BREEDING. 475 



secrete semen. It is not necessary, therefore, in experiment- 

 ing on a large scale, to have numerous males, but only that 

 they should be in the condition I have indicated." 



M. Coste does not entertain a doubt that breeds may be 

 crossed. Any two species of the Genus Salmo would no 

 doubt reproduce, by pressing the eggs from the one and 

 fecundating them with the milt of the, other. This may even 

 be the case with fish of different families, as the Perch and 

 Pike, or either of these with the Trout ; but the farther we 

 depart from the laws of nature in producing mongrels, the 

 more imperfect the progeny must be, and in either of the 

 cases above mentioned, it is likely the produce would be 

 mules incapable of reproduction. 



TREATMENT OF THE FECUNDATED EGGS. The time of incu- 

 bation varies according to the temperature of the water and 

 room in which the troughs are placed. I would recommend 

 that the latter be sixty-five or seventy degrees above zero. 

 M. Coste in his experiments, found that the eggs were 

 hatched in from thirty to sixty days, which is a much 

 shorter time than if the ova was deposited in a natural way 

 by the fish in. the brook. 



The eggs should be distributed evenly over the gravel in 

 the hatching-troughs, more thickly at the head where the 

 water enters. The unfecundated eggs should be taken out, 

 and any sediment forming on them removed with a soft 

 brush. 



M. Coste give the following interesting account of the 

 appearance and growth of the young in the egg, and its 

 escape from the shell. 



" In eggs vivified with the fecundating molecules, one may 

 see after a time, which varies according to the species and to 

 the temperature of the water, on the interior globe a line, 



