196 FISH CULTUBE 



eggs would flow over the top of the jar to the 

 floor. A mass of eggs will sometimes rise for 

 more than an inch above the top of the jar. It 

 is chiefly on account of this proclivity, nay cer- 

 tainty, of the eggs to rise that it is necessary to 

 have some one in attendance both day and 

 night. Another reason for constant supervi- 

 sion is the necessity for closely watching the 

 water-flow; as, owing to the small quantity 

 used, any slight obstruction in the faucet will 

 completely stop it. Sometimes, owing to 

 changes in the specific gravity of the eggs, the 

 flow must be increased or diminished. It often 

 happens that during the period of incubation 

 every faucet in a hatchery will have to be 

 changed within twelve hours. When a rise in 

 perch eggs occurs, the attendant must stop the 

 flow of water immediately, and with his hand 

 or a feather gently push the mass to the bot- 

 tom, where, after about five minutes, the eggs 

 will settle quietly. Then the water can be 

 turned on again slowly and cautiously. It may 

 be half an hour or more before a rise will oc- 

 cur again, if at all. 



