588 



WHEELER P. DAVEY 



except that the calculations are based on the supposition that 

 there were no beetles dead on the tenth day. This similarity is 

 still more marked between curves B and G. Except for a sunilar 

 hump between and 12 days, curve D resembles curves A and 



/<? 20 30 40 SO (SO 70 80 30 /OO P/ZYS 



Fig. 4 A series of curves showing the effect of X-ray doses smaller than the 

 threshhold dose. 



B. The hump is, however, much higher than in curve C. In 

 curve E the hump is still of the same shape as in curves C and 

 D (it is the integral of a probabihty curve) and covers a period of 

 12 days, but is considerably higher. In curve F the 'hump' is 

 the whole curve, except for a very fiat portion which represents a 

 single very resistant beetle. 



