b/O 



> 



bfl 

 bJO 



b£ 



C 

 «J 



)-r 



ID 



U 

 I 



X 

 C/2 



2x10 ^rontgen 

 ' ' ^100 



-50 



-10 



-0-5 



4 6 



Dose (in 1,000 rontgens) 



FIG. 1. Relation of frequency of dominant lethals produced in sperm to dose of 

 X-rays employed. A = percentage of eegs hatching; 1? = percentage of eggs produc- 

 ing adult flies; C = sex ratio. In each case the logarithm of the frequency is plotted 

 against dose; points experimental. Reproduced from Catcheside & Lea-" by kind per- 

 mission of the Editor of the Journal of Genetics. 



143 



