CARLTON. — COLOR CHANGES OF THE FLORIDA CHAMELEON. 265 



rarely found individuals which retained their green color in the light for 

 any great length of time. All such individuals, moreover, have eventu- 

 ally become dark brown, though in extreme cases the change has not 

 occurred until the animal had been exposed to the light as long as three 

 hours. Excepting these few instances, in which there has been a tem- 

 porary retardation of the brown state, it may be stated that generally 

 daylight induces the brown condition. 



The changes from brown to green and from green to brown are, how- 

 ever, by no means reversed repetitions of each other. The rate of change 

 differs according to its direction; in Table I are given a few characteristic 

 rates. As this table shows, the change to brown is accomplished much 

 more rapidly than that to green. However, a few individuals were found 

 in which the two rates were nearly equal ; thus in one instance the change 

 to green was accomplished in 14.5 minutes, that to brown in 13.5 min- 

 utes. Such cases as these are, however, rare, the great majority follow- 

 ing the general rule indicated in Table I. 



The chief facts thus far observed may be summarized as follows : The 

 dark brown condition of the skin is produced by the outward migration 

 of the pigment of the melanophores, a process which takes place in the 

 liglit and requires on the average about four minutes for completion. 

 The green condition is produced by the inward migration of the melano- 

 phore pigment whereby the ochrophore layer is exposed to the light, a 

 process which takes place in the dark and requires on the average about 

 twenty-five minutes for completion. 



2. Brown Condition. — ■ I shall now endeavor to make clear the factors 

 which are concerned with these two changes, beginning with the change 

 from green to brown. This change is, as I have said before, almost al- 

 ways accomplished quickly when a green animal is exposed to daylight. 

 Under these conditions it is conceivable that the change may be due 

 either to the direct action of the light on the melanophores or to changes 

 induced in these cells through the nervous system, which in its turn is 

 stimulated by light. 



My first experiments were directed to finding out whether the illumi- 

 nation of one part of the body had any influence on the color changes in 

 those parts which were not illuminated. To determine this 1 used a 

 dark-box about six inches long, two inches high, and five inches broad. 

 The box was blackened inside and was provided with a movable lid. At 

 one end of the box a small hole was made sufBciently large to admit the 

 head of a lizard of average size. The hole was surrounded by a collar 

 of loose black cloth, which could be made to fit snugly to the neck of the 



