62 



JACQUES LOEB. 



It is only this very low temperature at or very near the freezing 

 point which is injurious for the newly fertilized eggs. If the 

 temperature is a little higher, e. g., 7 C., the newly fertilized 

 eggs can live for weeks in it without being injured. Thus in the 

 experiment just mentioned some of the eggs were put immediately 

 after fertilization into a temperature of about 7 C. These eggs 



FIG. ii. 



developed very slowly but no abnormal embryos were observed 

 although some of the eggs were kept at a temperature of 7 C. 

 for four weeks. Those that were kept still longer at that tem- 

 perature suffered but probably not from the low temperature 

 but from the fact that the flasks in which they were kept were 

 closed. 



These experiments thus establish the interesting fact that 

 immediately after fertilization the eggs of Fundulus are rapidly 

 injured or killed when exposed to a temperature of o or a little 

 above, while after the embryo is formed they can be exposed to 



