LIGHT REACTIONS — METABOLISM MAY-FLY NYMPHS 431 



tive Epeorus nymphs was caused by treatment with alcohol (1 

 or 2 per cent) and decreased temperature (2° to 8°C.). These 

 reversed nymphs gave a survival time of 131 ± 6 minutes in the 

 same strength of cyanide. Their size average was 6.5 mm. 

 The difference in survival time is only 2.1 times the probable 

 error, and since the difference may have been affected by the 

 difference in size, too much emphasis cannot be laid on these 

 results. 



The survival time of eighteen nymphs of the same species 

 that failed to reverse in the alcohol-reduced temperature treat- 

 ment was 88 ± 3 minutes. Their average length was 6.1 mm. 

 The nymphs that were reversed by this treatment lived forty- 

 three minutes longer in the cyanide than those that remained 



TABLE 2 



Showing the relation between the sign of the phototactic reaction of Epeorus nymphs 

 and their resistance to potassium, cyanide 



NtTMBER 

 TESTED 



AVERAGE 

 LENGTH 



AVERAGE 



SURVIVAL 



TIME 



TREATMENT BEFORE KILLING 



NITMBER 

 TESTED 



AVERAGE 

 LENGTH 



AVERAGE 



SURVIVAL 



TIME 



Positive nymphs 



Negative nympha 



positive. Since this is 4.8 times the probable error, it must be 

 significant. 



The majority of the Epeorus nymphs treated with alcohol and 

 decreased temperature reversed their reaction to light and had a 

 slightly (perhaps questionably) lower rate of metabolism than the 

 control animals and a decidedly lower rate than those not re- 

 versed by the treatment. The nymphs that remained positi\'e, 

 although given the alcohol-low temperature treatment, appar- 

 ently had been stimulated by the alcohol, for they showed a 

 higher rate of metabolism than the control animals. This can 

 be explained by assuming that the alcohol acted as usual, first 

 stimulating and later depressing. If this be true, the fact that 

 alcohol plus reduced temperature was more effective than the 



