LIGHT REACTIONS — METABOLISM MAY-FLY NYMPHS 439 



TABLE 5 



Showing the comparative rate of carbon dioxide production of positive and negative 



nymphs under control conditions (p. 525) 



Number tested 23 pairs. Positive more, 21. Negative more, 2. 



Chart 1 Showing graphically the reaction of six untreated nymphs to light 

 from a 100-watt daylight Mazda (C2) placed 50 cm. from the experimental dishes. 

 The charting was done by an assistant from whose records these graphs were 

 copied. The scales show time in minutes. The left-hand side represents the 

 positive end of the dish, i.e., the end toward the light. Where the line is approx- 

 imately straight vertically the nymph was resting quietly. Curves and kinks 

 show movement which did not markedly change the position in the dish in respect 

 to light. Column 1 gives the reactions of a nymph that was predominantly 

 positive to light, which after twenty-three minutes' exposure gave more carbon 

 dioxide in the biometer than the negative nymph whose reactions are recorded in 

 column 2. Column 3 shows a nymph made positive by long exposure to light. 

 In this case the reversal came suddenly. Column 4 gives the same result ob- 

 tained by a different method. Perhaps column 3 represents a ' tropic' and column 

 4 a 'trial' reaction. Columns 5 and 6 show the reactions of two nymphs that 

 were tested in the biometer before exposure to light. The animal with the higher 

 rate of carbon dioxide production became positive. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 26, NO. 3 



