EFFECT OF X-RAYS ON TRIBOLIUM CONFUSUM 



583 



MAM 



never more than 4 per cent. Beetles rayed 500 at 50 KV. 



25"' 



were practically all dead in 15 days. Beetles rayed larger doses 



were all dead in less than 15 days. Therefore no correction for 



normal death rate of the X-rayed beetles was considered 



necessary. 



It w^as found that while all the beetles in a given box did not 



die at the same moment, there was very narrow range of time 



during w^hich most of them died, thus suggesting that we were 



dealing with a quantitative effect which could be studied to 



some good. For example, the results given more in detail in 



tables 1 and 2 and in figure 2, show that if the dose was 15,500 



MAM 



25^ 



at 50 KV. all the beetles were dead at the end of the 



raying; if the dose was 2000 MAM at 50 KV. practically all 



Zio'' 



the beetles died between the third and the sixth days after ray- 

 ing, while half of them died between the fourth and fifth days; 



MAM 



if the dose was 500 



252 



at 50 KV. death took place between 



the fourth and the ninth days, while half of them died between 



MAM 



the sixth and eighth days. Doses less than 500 — at 50 



KV. were not fatal to all the beetles. 



Now if the percentage of dead beetles is plotted against the 

 time which has elapsed since they were X-rayed, it is evident 



TABLE 2 

 MAM 



Beetles rayed 500 ,^„ at 50 /vKrms 



Z5^ 



THE JOURNAL OF EXPERIMENTAL lOOLOGY, VOL. 22, NO. 



