EFFECT OF X-RAYS ON TRIBOLIUM CONFUSUM 



587 



Curves like figure 2 have been obtained time after time, the 

 only difference being in the height of the ordinates and the slope 

 of the family of curves. Figure 3 shows a typical curve of this 

 sort. It will be noticed that in spite of the difference in the 

 ordinates, the sharp break in the curve occurs at the same dosages 



At 50 kilovolts the lowest dose of X-rays which is fatal to all 



the beetles in 500 -' In order to explore the field below 



this dose, 1100 beetles were gathered from the same brooder at 

 the same time and packed into boxes of 25 each with sterile corn- 



Fig. 3 A typical curve showing days-life plotted against the logarithm of 

 the X-ray dose at 50 KVrms- 



meal, and these boxes were divided into 7 groups of 8 boxes 



each, and one group of 4 boxes. 



One group of 8 was kept as a control. The others were rayed 



MAM 

 100, 200, 250, 300 ^^ at 50 KV. respectively. The group of 

 25 



4 was rayed 500 at 50 KV. The results are plotted in 



figure 4, curves A, B, C, D, E, F, G. 



It will be noticed that there is but little difference between 

 curves A and B. Except for a small hump between and 10 

 days, there is but httle difference between curves A and C. 

 This is brought out in curve G which is the same as curve C, 



