CARLTON. — COLOR CHANGES OF THE FLORIDA CHAMELEON. 273 



Veranus, Uromastix, and Agame, according to Thilenius ('97), just the re- 

 verse takes place, — an inward migration in the light, and an outward 

 one in the dark. That Thilenius's observations are probably cor- 

 rect is shown by the fact that similar conditions have been described 

 by Filippi ('66) for Stellio, and by Wiedersheim (Hoffmann, '90), for 

 Phrynosoma. Apparently lizards fall into two classes in this respect : 

 those with an outward migration of pigment in the light, and those with 

 an inward migration under like circumstances. 



Although Anolis agrees with Chameleon in that its melanophore pig- 

 ment moves outward in the light and inward in the dark, it differs funda- 

 mentally in other respects. I believe I have found satisfactory evidence 

 to show that the outward migration of pigment in Anolis is dependent on 

 the action of the sympathetic centres. The investigations of Briicke 

 ('52), Bert ('75), Keller ('95), and others on the effects of nerve cutting 

 and local stimulation by light in Chameleon have shown conclusively 

 that the outward migration in this form is independent of nerves and 

 due to the direct stimulation of the melanophore cells by light. On the 

 other hand the inward migration of pigment in Anolis is a return of 

 the cell to a resting state, dependent neither upon direct stimulation nor 

 nerves, while in Chameleon this change has been shown beyond a doubt 

 (Keller, '95, p. 137) to depend upon nerves. Thus, so far as the rela- 

 tion of the color changes to nerves is concerned, Chameleon and Anolis 

 are the reverse of each other. 



From the experiments of Briicke ('52), Bert ('75), Krukenberg ('80), 

 and Keller ('95) on cutting the spinal cord of Chameleon, it would seem, 

 since the skin became black posterior to the cut, that the spinal nerves 

 control the inward migration of the pigment in this reptile. As already 

 shown, such an operation in Anolis has little or no effect on the final 

 change of color, and hence the sympathetic nerves must be assumed to 

 act in Anolis. 



Thus in a second fundamental particular Anolis differs from Cham- 

 eleon. Anolis also differs not only from Chameleon, but also from all 

 other lizards, so far as is known, in that the migration of the pigment 

 in its melanophores is not directly influenced by light. It has been 

 abundantly shown that the outward migration of the melanophore pig- 

 ment in Chameleon is dependent upon the direct action of light, and 

 Thilenius ('97, p. 539) has maintained that direct light stimulation also 

 occurs in Varanus, Uromastix, and Agame. Nothing of this kind has 

 been observed in Anolis. Here the inward migration might be sus- 

 pected to occur under local stimulation, but it takes place in the dark 

 vol. xxxix. — 18 



