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PROCEEDINGS OF THE AMERICAN ACADEMY. 



from the fact that the change to green was very slow, the heat at 

 20° almost counteracting the change that takes place as the result of 

 darkness. 



At 25° the animals changed more quickly to green than at 20°, show- 

 ing that at a higher temperature the heat had less retarding effect. The 

 same was true, but still more noticeably, at 30°. 



At 35° the heat checked the coming on of the green more than at 

 30° or even 25°, though the condition at 35° was followed by stages 

 (40° and 45°) at which the animals were persistently greenish even in 

 the fight. Why retardation should occur at 35° is not clear, for one 



TABLE I. 



Rate of Change of Anolis from Brown to Green 

 AT Different Temperatures. 



would expect a still more rapid rate than at 30°. However, subsequent 

 tests of this invariably showed that the rate was persistently slower at 

 35° than at 30°, and hence we cannot conclude that this record was due 

 to faulty observation. Possibly the increase of temperature which be- 

 tween 20° and 30° may have acted on the melauophores of the skin in 

 one way, e. g., directly, may at 35° have influenced them in another 

 way, e. g., indirectly through nerves. But to this question we have no 

 definite answer. 



At 40° and 45° the animals became greenish and remained persistently 

 60. As this happened not only in the dark but also in the light, where 



