440 



W. C. ALLEE AND E. R. STEIN, JR. 



TABLE 6 

 Showing the effect of long exposure to light upon carbon dioxide production 



EXPERIMENTS WITH HYDROCHLORIC ACID 



1. Effect on negative nymphs 



As with the other species studied, hydrochloric acid was one 

 of the most effective reagents in causing reversals. In one set 

 of carefully controlled, fully plotted experiments there were a 

 total of 220 control or preliminary readings lasting from fifteen 

 to ninety-three minutes. Of the nymphs thus tested, thirty-seven 

 were or became positive without other treatment than exposure 

 to light. This is 17 per cent of the number tested. 



In this same series of experiments 125 nymphs that had been 

 consistently negative through a preliminary testing period of at 

 least fifteen minutes, were treated with N/25 hydrochloric acid. 

 Under this treatment, seventy-five nymphs, 60 per cent, became 

 positive. Of the fifty nymphs that did not reverse, twenty-five 

 were kept under observation for less than twenty-five minutes 

 and only two were kept until they died. If it had been the pur- 

 pose of the experiments to ascertain how many nymphs could be 

 reversed by the treatment, doubtless about 90 per cent would 

 have become positive before death resulted. 



The typical effect of the acid upon the fight reactions of these 

 nymphs is shown in chart 2. The graphs show that the nymphs 

 may reverse soon after being placed in the acid or the reversal 

 may come only after long exposure. Forty-eight per cent of the 

 reversals came within fifteen minutes, but reversals occurred 

 after seventy minutes' treatment. Death frequently followed 

 close upon the later type of reversals. 



