PARKER AND STARR ATT. — COLOR IN ANOLIS CAROLINENSIS. 459 



was necessary to keep them as nearly in one state in this respect as 

 possible. Since the lizards chase one another when together, and thus 

 introduce disturbing factors, each one was placed in a small oblong 

 box painted black inside and resting directly on the top of the water- 

 chamber ; each box was covered by a plate of glass. When the light 

 was turned on, the rays, after passing through the heat screen and llie 

 glass top of the small box, fell upon the lizard with an intensity of 

 about 115 candle-metres. The top of the water-chamber was large 

 enough to allow six lizards to be experimented upon at once, and that 

 number was usually employed. 



Ill, Experiments. 



From what has already been stated by Carlton (:03) it is evident that 

 in testing the effect of temperature changes on Anolis it is necessary to 

 exclude light, or at least to control it so that its influence will not enter 

 into the final result. The constant-temperature box, already described, 

 was planned with this in view. 



Our first experiments were designed to determine the rate of change 

 from brown to green at different temperatures. For this purpose six 

 lizards were placed, one in each of the six small boxes on the water- 

 chamber, and after the whole apparatus had come to the requisite tem- 

 perature the rate of change was ascertained in the following way : The 

 incandescent lamp was lighted and the lizards were kept under its 

 influence until they were thoroughly brown. Then the light was turned 

 out, and the length of time needed for the change to green was recorded 

 for each individual. To ascertain when this had occurred the box was 

 from time to time momentarily illuminated by the lamp and an observa- 

 tion was made through the small glass window. As a rule, four such 

 determinations on each of six animals were made for each temperature, 

 so that in the following table the average time for a given temperature is 

 based on twenty-four records. 



Table I shows the average rates at which these lizards changed from 

 brown to green at temperatures ranging from 10° C. to 45° C. 



At 10° the animals remained brown in the dark as well as in the 

 light. Hence at this temperature heat was the controlling factor. 



At 20° the animals slowly changed to green. Since at this tem- 

 perature they remained brown in the light, it is evident that the change 

 to green is not dependent upon heat, but upon the absence of light. 

 That the heat, however, had some influence at this stage is seen 



