LIGHT REACTIONS METABOLISM — MAY-FLY NYMPHS 449 



EXPERIMENTS WITH ALCOHOL AND STRYCHNINE 



Ethyl alcohol had less marked effect in causmg reversals among 

 these Heptageninae than with the species used in the first part 

 of the work. In twenty-five well-studied cases, only five nymphs 

 were by treatment with 2 per cent solution reversed. Of the 

 fifty-two accompanying preliminary or control readings, one 

 nymph became positive. When alcoholic nymphs were tested 

 in the biometer (table 14), it was found that alcohol acts here 

 according to its usual effect as a narcotic, first stimulating and 

 later depressing. 



Some typical results obtained with the alcohol treatment are 

 given in chart 4. This shows two tracings of the reactions of 

 nymphs that were not reversed by the treatment and of one that 

 was, together with a type of control reaction which occurred 

 frequently. 



Some preliminary experiments with strychnine showed a 

 marked increase in the activity of the nymphs without a reversal 

 of their light response. The animals usually remained at the 

 negative end of the dish in almost continual motion. In the 

 biometer, they usually showed a markedly increased carbon 

 dioxide production. 



I am not able to state why these nymphs did not reverse their 

 light reactions, but offer these results with alcohol and strychnine 

 as evidence that all stimulation and depression do not cause 

 reversals in phototaxis. 



Chart 3 Showing the light reactions of ten nymphs treated with potassium 

 cyanide together with three preliminary test periods and one complete control. 

 In the cases where the preliminary and control graphs are not given it is under- 

 stood that they are in no essential respect different from those shown. In order 

 to economize space the time spent in changing from water to cyanide is not fully 

 shown as it was in chart 2. Where such a change is indicated it must be 

 understood that two or three minutes elapsed. In all cases given in columns 5 and 

 6 the control, with which the carbon dioxide production of the treated njanphs 

 was compared, is not given in the chart. For text reference see p. 535. 



