EFFECT OF X-RADIATION ON CUMINGIA EGGS. 



215 



free-swimming larvae 381 minutes after fertilization. 63 shows 

 an increase, 615 a decrease over the control. 



Several observers have noted a stimulation to cell division 

 when eggs have been fertilized by sperm subjected to an exposure 

 of short duration. This observation can now be recorded for 

 Cumingia. It is unfortunate that we have no samples of the 

 experiment between the 74-minute and 381 -minute stages of 

 development in order to trace this through the cleavage develop- 

 ment. The longer irradiation shows the expected retarded de- 

 velopment, this length irradiation being harmful. 



The C series consisted of radiated eggs fertilized by normal 

 sperm. As stated before the control is the same as for series B. 

 The following is a tabulated result from a study of the samples 

 taken. 



TABLE III. 



From this table it is evident that even a slight irradiation of the 

 unfertilized egg causes retardation in the rate of cleavage and 

 the development. That they do not develop shows that some- 

 thing has been interfered with in the metabolism of the embryo. 

 Fertilization, however, appears normal in every respect and the 

 polar bodies are given off normally. 



The D series consisted of radiated eggs fertilized by radiated 

 sperm. The control was the same as for B. Samples were taken 

 similar to the other series. A study of the samples gave the 



following results. 



Fertilization and maturation are slower in both irradiated sets 



than in the control. The shorter radiation, 74 minutes after 

 fertilization shows a retardation over the control. The 15 minute 



