FISH-BRBEDINa. 477 



been hatched; others on the contrary, such as the Salmon 

 and ^ the Trout, weighed down by their enormous umbilical 

 bladder (figure 2), can only move with great difficulty, and 

 remain lying on one side, or even on the bladder itself. 

 Some few attempt to move from one place to another, but 

 soon give up the effort. 



Vsiii/ 



" The time for hatching is not the same with all species. 

 Some, like the Pike, hatch at the end of eight, ten, or fifteen 

 days ; others, like the Salmon, take from a month and a half 

 to two months. 



"Besides development is more or less hastened, according 

 as the temperature of the water in which they are laid is more 

 or less elevated. Pike's eggs placed in a vase, the water of 

 which without being renewed was exposed to the sun's rays, 

 hatched in nine days ; while others of the same spawning, 

 placed in the shade in water constantly renewed took eighteen 

 to twenty days to hatch. It required also twenty days to 

 hatch eggs of the ombre, which, more favorably placed, 

 hatched in twelve to fifteen days. Still greater variations of 

 time appear in the incubation of other species of the Salmon 

 family. In running water of a warm temperature, the eggs 

 of Salmon and Trout will hatch in about thirty days, while 

 the same eggs in a cold stream will take seven or eight 

 weeks. The term of incubation may even extend to a hun- 

 dred and ten days, as was proved by the experiments made in 



