CARLTON. — COLOR CHANGES OF THE FLORIDA CHAMELEON. 2G3 



The nielanophores in the green skin (Fig. 3, mela'ph.) differ from 

 those in the brown skin in tliat their branches seem to have disappeared, 

 the main processes terminating in rounded ends. Hitherto it has been 

 a question whether the branches are really drawn in like the pseudopodia 

 of an amoeba, or whether the pigment granules simply move down the 

 branch into the process, or into the cell, thus making it difficult to see 

 the transparent branch. The latter condition is now held to be true for 

 the chameleon, as was first maintained by Briicke ('52, p. 201). In 

 attempting to ascertain the condition in Anolis I partially depigmented 

 some sections of skin and stained them in Delafield's haematoxylin. In 

 these sections I could see clearly the empty branches extending out from 

 the region where the pigment ceased, to the base of the epidermis, and I 

 was thus convinced that the branches are not withdrawn, but simply 

 emptied of pigment. In the green condition of the skin the cell body of 

 the melanophore, as might be expected, is more densely filled with 

 pigment granules than in the brown state. 



It is clear from the foregoing account that the active pigment changes 

 accompanying the color changes in the skin of Anolis occur only in the 

 melanophores. In this respect these changes are like those in Varanus, 

 Uromastix, and Agame as described by Thilenius ('97, p. 532). In the 

 dark brown state the pigment of the melanophores fills the processes and 

 branches of these cells to their distal extremities, thus producing an 

 almost continuous dark layer immediately under the epidermis and ex- 

 ternal to the ochrophore layer. It is this dark layer that gives to the 

 animal its dark color. la the green state the dark pigment of the outer 

 branches of the melanophores has retreated into the deeper processes, or 

 even into the cell body beneath the ochrophore layer, thus exposing this 

 layer to the light. As microscopic preparations show that the material 

 of the ochrophore layer reflects a bright bluish-green light, it is probable 

 that the pea-green color characteristic of this state is due chiefly to 

 reflexion from this layer, though the transparent epidermis may modify 

 more or less the color that would otherwise appear. 



The outward migration of the melanophore pigment granules of Anolis 

 in the light and their inward migration in the dark is like that recorded 

 by almost all observers for the African chameleon. It is the reverse of 

 the condition described for Stellio by Filippi ('66), for Phrynosoma by 

 Wiedersheim (Hoffmann, '90, p. 1353) and for Varanus, Uromastix, and 

 Agame by Thilenius ('97). In all these reptiles the melanophore pig- 

 ment moves inward in the light, and outward in the dark. 



