APPENDIX IX. 317 



draw the fish slowly over the pan to the opposite edge, 

 letting the roe fall in the water, and fasten the other end 

 of it, as before, to that edge of the pan. You will then 

 have the roe suspended in the water in such a way that it 

 cannot get together and stick, and suffocate itself, as it 

 surely would if it had a chance. Shake the pan a little. 

 In an hour rinse the eggs, change the water twice a day, 

 and in twenty days, if tlie water is not too cold, your eggs 

 will hatch. 60 degrees Fahrenheit is a very good tem- 

 perature to hatch them in, but they will stand a tempera- 

 ture as high as 85 degrees, at which point their develop- 

 ment is very rapid. At 95 degrees they die. If you put 

 a couple of large stones in the pan, to rest the ends of 

 the roe on, it is better than to stick them to the edge of 

 the pan. 



The development of the perch embryo is exceedingly 

 interesting. A very singular feature of it is the movement 

 of the embryo in the egg, which begins almost as soon as 

 the form of the fish is visible. The little creature jumps 

 from one wall of the egg to the other, with a quick spas- 

 modic movement, like that observed in the animalculae in 

 a drop of water under a very high magnifying power. 

 This motion is as regular, when the eggs are not dis- 

 turbed, as the ticking of a watch, and never ceases, day 

 or night, except when the eggs are shaken, when, by an 

 instinctive consent, every fish stops as if by magic. In a 

 second or two the movement begins again. 



The viscous matter which envelops the eggs and holds 

 them together is finally wholly absorbed, and the eggs fiiU 

 apart. They now consist of merely a frail shell, contain- 

 ing the embryo. This shell easily breaks, and the young 

 perch is set free. He is very small, not more than half as 

 large as a black bass just hatched, or one fourth as large 

 as a whitefish an hour old. 



The roe of the yellow perch comes in folds from the 



