264 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



III. The Physiology of the Color Changes. 



1. Introductory. — As previously stated, Lockwood ("76) has observed 

 — and I can abundantly confirm his observations — that Anolis carolin- 

 ensis when in confinement during the winter is usually dark brown by 

 day and pea-green at night. That this change is not simply rhythmic in 

 character, but is dependent upon factors in the environment, is seen from 

 the following experiments. When an Anolis that has turned green at 

 night is placed in a dark-box so that it remains in the dark after day- 

 break, it retains its green color until exposed to daylight, whereupon it 

 rapidly turns brown. If, on the other hand, a brown Anolis is exposed to 



TABLE I. 



illumination from a strong arc light (a gas-light is not sufficient) as even- 

 ing comes on, it retains its former color and does not become green as 

 long as it remains in a strong light. Thus the color changes are not 

 rhythmic in correspondence with day and night, but depend upon the 

 immediate effects of some factor in the environment, presumably light. 



When a brown Anolis is put in the dark it invariably becomes green. 

 This experiment I have repeated with perhaps one hundred animals, each 

 one being tried several times, and I have never found an exception to 

 this rule. The absence of light is therefore a means of inducing the 

 green state. 



When a green Anolis is put into the light it almost invariably becomes 

 brown. I have repeated this experiment many times, and I have only 



