April, 12] HUNTER: ROENTGEN RAYS 191 



dealt with eggs of Margaropus annulatus in which incubation had 

 just begun. These eggs began hatching from 20 to 25 days after 

 exposure. Eventually from' 75 to 90 per cent hatched. There was 

 a hatching of 80 per cent in the controls. This experiment therefore 

 corroborates the conclusion from the prior experiment regarding the 

 harmlessness of the rays to the eggs. 



Later series of experiments were performed with the female ticks 

 which were depositing eggs, ^^^th females which were engorged but 

 which had not begun the deposition of eggs, and with unengorged 

 larvae. The variation in the length of the exposure and other details 

 were similar to those in the experiments that have been described. 

 In all of these cases no effects from the rays were discernible. 



In further experiments other species of ticks were utilized including- 

 Argas miniatus and Dermacentor venustus. In no case was any defi- 

 nite indication obtained of any effects whatever from the rays. 



Somewhat later experiments were conducted at New Orleans with 

 the sugar cane mealy bug, Pseudococcus calceolarice. In this work a 

 new factor was added. This was the determination of whether the 

 effects of the rays tend to accumulate. It seems to be well established 

 that in the case of human beings the effects accumulate in regular 

 progression, that is that an exposure of one second on ten different 

 days has exactly the same effect as an exposure of ten seconds in one 

 da3\ In the case of the sugar cane mealy bug, gravid females were 

 exposed for 1, 2, 4, and 8 minutes and also for 1 minute on 1, 2, 3, 

 4, 5, 6, 7 and 8 days. All exposures were at a penetration of 5, accord- 

 ing to the Benoist radio-chronometer. In these experiments the 

 time elapsing from exposure to hatching varied without any apparent 

 connection with the number of days exposed. The control females 

 yielded eggs which hatched in 3 days and this was the case with eggs 

 from 1, 2, 5, 7 and 8 day exposures. 



Similar experiments with the eggs of Culex pipiens were performed. 

 The accumulated exposures did not yield any more definite results 

 than in the case of the other species. 



Up to this point our experiments (except those with the rice weevil) 

 were concerned primarily with the determination of the possible 

 destructive effect upon the insects in various stages and especially 

 upon the viability of the eggs. A series of observations was made,, 

 however, more particularly to determine the effect upon the function- 

 ality of the sexual organs. In these experiments several species 

 including the boll weevil, were tried but the most satisfactory results 

 were obtained with the sugar cane borer, Diatrcea saccharalis. In 

 this case all of the specimens utilized were bred to maturity under 

 isolation to obviate the possibility of accidental fertilization. Exposed 



