THE BLINDNESS OF THE CAVE FA I \ A. 



61 



A second lot of eggs were put on ice four and a half hours after 

 fertilization when they were in the 4-cell stage or beyond. These 

 eggs were just as sensitive to the effect of the low temperature 

 as those put on ice immediately after fertilization. 



This experiment was repeated four times with the same result. 

 In another experiment the eggs were allowed to develop to 

 about the 128-cell stage at normal temperature before they 

 were put into a temperature of o (about fifteen hours after 

 fertilization). Eggs that were kept at that low temperature for 



BEATING 

 HEftRT 



FIG. 10. 



two days were still able to develop into normal embryos but 

 those that had been kept three days at the temperature of from 

 o to 2 C. were practically all dead. 



When the eggs were put into a temperature of from o to 2 C., 

 after the embryo was formed and the circulation established, 

 they could resist the low temperature for weeks. When put 

 back to normal temperature they recovered and developed 

 normally. 



Further experiments are required to ascertain more accurately 

 when the eggs become immune to the temperature of from o to 2. 



