6o 



JACQUES LOEB. 



egg of the same fish is exposed to such a low temperature imme- 

 diately after fertilization or when the eggs are in the process of 

 early segmentation they suffer severely. 



Thus in one experiment the eggs of Fundulus (fertilized with 

 sperm of their own species) were distributed into a number of 

 Erlenmeyer flasks and put on ice immediately after fertilization 

 and kept at a temperature of between o and 2 C. After four 



BEATING HEART 



FIG. 9. 



hours, seven and a half hours, twenty-three hours, thirty-two 

 hours, forty-eight hours, sixty-four, and ninety-six hours one lot 

 was returned to room temperature. All the eggs taken out after 

 forty-eight hours or later were dead; few of those taken out 

 after thirty-two and twenty-three hours survived. A consider- 

 able percentage were abnormal and resembled the heterogeneous 

 hybrids between heteroditus 9 and Menidia cf . Most of those 

 taken out after four and seven and a half hours survived, but 

 about 20 per cent, to 30 per cent, were abnormal. Among the 

 abnormal embryos a number of blind fish were found. 



