RADIATION AND FERTILIZING POWER. 



483 



TABLE V. 



THE RELATION OF DOSAGE OF RADIATION TO THE DEGREE OF 

 INHIBITION OF CLEAVAGE. 



Figures 8-15 represent sperm dilutions 5 8 ~5 15 per cent. 



the degree of reduction in each case is more marked in the 

 weaker suspensions, e.g., exposures of less than one minute 

 reduce the fertilizing power 50 per cent, in dilutions of ^ 12 per 

 cent, to | 15 per cent. The same exposure reduces the fertilizing 

 power of dilutions of ^ 8 per cent, to i 10 per cent, only 10-20 

 per cent. Five and ten minute exposures reduce the fertilizing 

 power to 2 per cent, or less in all dilutions. (See Figure 3.) 



Discussion. The loss of fertilizing power of normal sperm 

 suspensions occasioned by dilution and staling is greatly acceler- 

 ated by exposure to ultraviolet radiation. The greater the 

 dilution of the sperm, the more rapid is the reduction of ferti- 

 lizing power, and the more delayed and abnormal is the cleavage. 

 Dosage of radiation is also a factor in determining the degree of 

 inhibition of fertilizing power. Motility is reduced and the 

 sperm forms aggregations which are large and irregular, and 

 recall those described by F. R. Lillie, '126, '13, 'i$a, Just, '19, 

 J. Loeb, '14, and Sampson, '22. Exposure to ultraviolet radi- 

 ation appears to increase the surface adhesiveness of sperm, 

 inducing agglutination, a change probably accompanied by a 

 change in permeability of the sperm membrane. (See also F. 

 R. Lillie, '13, in this connection.) 



Although motility is considerably interfered with, the loss of 

 fertilizing power does not necessarily parallel the loss of motility. 



