RADIATION AND FERTILIZING POWER. 



481 



1/240,000 per cent, is exposed to radiation from the mercury arc 

 for periods of 2 and 5 minutes, it becomes evident that the more 

 dilute suspensions are more susceptible to reduction in fertilizing 

 power than the more concentrated suspensions. Nonradiated 

 controls show 100 per cent, cleavage in all dilutions up to 1/30,000 

 per cent., in which case 60 per cent. -of the eggs cleave normally, 

 15 per cent, abnormally, and 25 per cent, fail to cleave. When 

 a dilution of 1/240,000 per cent, is reached the total cleavage 

 amounts to but 9 per cent., when sperm are used immediately 

 after radiation to fertilize normal eggs. Dilution of sperm is 

 certainly a factor in modifying its fertilizing power, even in non- 

 radiated suspensions. 



Table IV. shows the effects of radiation on cleavage. It will be 

 seen that membrane formation is possible, with less dilute 

 suspensions of sperm when radiation does not exceed 2 minutes. 

 That the degree of inhibitory effect of radiation increases with 

 dosage is indicated here. 



TABLE IV. 



THE EFFECT OF RADIATION OF SPERM ON THE RATE OF CLEAVAGE OF EGGS. 

 (Eggs were fertilized immediately following dilution and radiation of sperm.) 



Dilutions as before, n and 15 are averages of three experiments each; 14 of 

 two; and the rest, one each. 



A Advanced cleavage. C Membranes only. 



.B Slow cleavage. D No membranes. 



That the degree of the effect of radiation is roughly proportional 

 to dosage is better shown in Table V., where the exposures were 

 briefer. In these experiments, on the day following radiation of 

 sperm, swimming preplutei were found in radiated lots, only 

 with sperm dilutions of 8 per cent. ; early gastrulae were plentiful 

 i n 19-114 per C ent., and scarce in | 15 - 18 per cent. In the control 

 series (nonradiated) all dilutions showed swimming preplutei. 



