CULTURE OF YELLOW PERCH 195 



period of incubation. There are no eggs which will 

 stand as much rough handling. If they become cov- 

 ered with mud they may safely be taken from the jars 

 and washed in tubs of water. If any portion of the 

 string should die it may be cut or broken away with- 

 out any harm whatever to the parts which are alive. 

 The one feature of first importance is constant at- 

 tention day and night. The jars may be nearly filled 

 with eggs, and although they seem to be resting in 

 a heavy mass there need be no apprehension of 

 smothering. Only a very slight flow of water is re- 

 quired, but little more in fact than is needed to fill 

 the tubes, preventing air becoming mixed with it, 

 and to flutter or oscillate slightly the mass. 



As the eggs are semibuoyant, and at times 

 actually buoyant just before hatching, it is im- 

 portant that a screen of mosquito-wire be set 

 completely around the inside of the top of the 

 jar. The change from semibuoyancy to buoy- 

 ancy is very sudden, and occurs usually just as 

 the eggs are beginning to eye. At this period 

 the gelatinous material, which is tough and 

 strong when the eggs are first deposited, 

 softens, or as it is termed "rots," the string 

 breaking into pieces and rising to the surface. 

 Were it not for the screen described above, the 



