342 A. FRANKLIN SHULL. 



of these cool dishes is an estimated average. Because fewer 

 eggs were to be expected at such low temperatures, several 

 dishes were kept at low temperature for every one at room tem- 

 perature. 



There is no question here that the eggs are laid more largely 

 at the surface when the temperature is high. The experiment 

 was repeated on a small scale with the same result. 



Effect of Temperature upon the Viability of the Fertilized Eggs. 



Freezing. Freezing of fertilized eggs was designed as a prac- 

 tical measure only, in order to induce those eggs to hatch which 

 would not otherwise hatch. The attempt failed, however, as 

 shown by the following tests. 



In the first experiment about 244 eggs that remained unhatched' 

 after hatching had ceased for 12 days in the lot of eggs to which 

 they belonged, were divided into two approximately equal groups. 

 One group was frozen over night by immersing, in a closed vessel, 

 in a brine-ice mixture and the other was kept in water at ordinary 

 temperature. Of the frozen lot none hatched in 19 days there- 

 after. Of the control lot at room temperature, one hatched in 

 10 days after the beginning of the experiment, none thereafter 

 Freezing did not facilitate the hatching. 



In the second experiment about 230 eggs that remained un- 

 hatched for 14 days after hatching of the eggs in the same lot 

 had practically ceased were similarly divided into two groups, 

 one of which was frozen over night and the other kept at room 

 temperature. None of these eggs in either lot hatched in 19 

 days, after which time observation ceased. 



From these experiments it appears that fertilized eggs not 

 ordinarily capable of hatching can not be made to hatch by 

 freezing. 



Low Temperature Above Freezing. Two lots of fertilized eggs 

 from the same source and of approximately equal numbers were 

 kept at different temperatures from the time they were laid until 

 hatching was nearly complete. The eggs were laid between 

 November 29 and December 8. One lot was kept at room tem- 

 perature. The other was set outside on a window sill where 

 daytime temperature, as shown by a thermometer placed beside 



