247 



Considering first the four experiments forming Series A, it will be 

 noticed that in each case the eggs fertilized later completed the 4-cell 

 division in a shorter time than those fertilized earlier. Thus in Exp. 1, 

 eggs fertilized one hour after being removed fi-om the animal into sea- 

 water took 115 minutes to complete the 4-cell division, those fertilized 

 after two hours in sea- water took 108 minutes, those after three hours 

 101 minutes, and those after four hours only 100 minutes. The figures 

 for the other three experiments show a similar increase in rate. This 

 point has already been recorded by Morgan (9), although he made no 

 exact observations on the times of segmentation. With regard to the 

 later development, the hatching rates of this series show that the 

 second fertilization continued to have a more rapid rate than the first 

 ones. In Exps. 1 and 2, the parallel with the earlier segmentation 

 ceased here, for in the latest fertilized eggs the rate of development 

 of the embiyo slowed down again. In Exp. 3, on the other hand, the 



