THE NEW ABT OF BREEDING FISH. 63 



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 be- 

 ing 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 incuba- 

 tion of other species of the salmon family. In run- 

 ning water of a warm temperature, the eggs of sal- 

 mon 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 ex- 

 tend to a hundred and ten days, as was proved by 

 the experiments made in Scotland, by Mr. Shaw, to 

 which I have referred in the introduction. 



During their change the eggs should not be left 

 to themselves ; they require, on the contrary, a cer- 

 tain watchfulness and frequent visits, in fact, such 

 care as can be easily bestowed by the aid of the 

 hatching apparatus which I use. 



Whether the artificial streamlets, which I propose, 

 be used, or in preference to them any other mode, 

 one precaution should always be taken ; the eggs 

 should never be heaped upon one another. Their 

 accumulation prevents a proper surveillance of aU of 

 them, and besides may retard or even prevent their 



