62 THE NEW AKT OF BREEDING FISH. 



hatching besides the quick movements of the young. 

 The outer envelope of the egg becomes a httle 

 opaque, and as it were furfuraceous. With other 

 species with which I have made observations, this 

 sign does not appear so plainly. At last a little 

 opening is made in the shell, and that part of the 

 embryo next the opening comes through it. Ordi- 

 narily the tail or the head first appears, but some- 

 times it is the umbilical bladder. 



Whatever part may be first disengaged, more 

 than half the body still remains imprisoned, and the 

 efibrts of the young fish are unceasing, till after sev- 

 eral hours it frees itself from the shell. This mem- 

 brane, which has protected its development, hut has 

 not served to form any part of its organs, being now 

 cast off, either is decomposed where it lies, or is car- 

 ried ofl" by the current. 



Certain kinds, like the pike and the ferrat, begin 

 inunediately to range about in the waters where they 

 have just been hatched ; others on the contrary, such 

 as the salmon and the trout, weighed down by their 

 enormous umbilical bladder (pi. 2,Jig. 9), can only 

 move with great difficulty, and remain lying on one 

 side, or even on the bladder itself. Some few at- 

 tempt to move from one place to another, but soon 

 give up the effort. 



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. 



