260 PROCEEDINGS OF THE AMERICAN ACADEMY". 



Anolis carol inensis Cuv„ This lizard belongs to the family Iguanidae 

 Cope (:00), and thus is not a true chameleon, although, as its popular name 

 indicates, it possesses remarkable properties in the matter of the color 

 changes of its skin. 



A large number of living specimens of Anolis were obtained during 

 the winter of 1902-03 from a dealer in Jacksonville, Florida. They 

 lived well in confinement and exhibited characteristic color changes. As 

 Lockwood ('76, p. 12) has already observed, they are as a rule dark 

 brown during the day and pea-green at night. These extremes, with a 

 series of transitional tints running through shades of brown and yellow 

 to green, were the chief colors regularly noticed. Whether these changes, 

 which were observed during the winter in the laboratory, are also char- 

 acteristic of the animals in their natural haunts, I am unable to say. As 

 far as I have been able to observe, the play of colors so conspicuous in 

 the African chameleon is rarely if ever approached in Anolis. Lockwood 

 ('76, p. 13), however, has described conditions which more nearly re- 

 semble those of the African chameleon than any I have seen. In this 

 respect Anolis is much simpler, and consequently much more satisfactory 

 for experimental work, than the true chameleon. 



To insure precision in my work, I not only chose a lizard with a rela- 

 tively simple color change, but I experimented as a rule only on definite 

 portions of its skin, namely, the uniformly tinted areas which cover the 

 sides of the animal's body. These regions showed the full range of 

 color change from dark brown to pea-green, and proved to be conven- 

 ient areas to deal with. Unless otherwise stated, what is contained in 

 the following account refers to the skin of these regions. I shall begin 

 with a description of the histology of the skin in the brown and in the 

 green states, and I shall afterward take up the physiology of the changes 

 concerned in the production of these two states. 



The subject of this research was suggested to me by Dr. G. H. Parker, 

 under whose guidance I have carried out the work. 



II. The Histology of the Color Changes. 



The skin of Anolis carolinensis, like that of other reptiles, consists of 

 a relatively thin epidermis, in which a horny layer (Fig. 1, st. cm.) and 

 a mucous layer (st. mm.) can be distinguished, and a derma (drm.), com- 

 posed chiefly of interlacing connective-tissue bundles. Among other 

 structures the derma contains numerous chromatophores, and other less 

 clearly definable pigment masses. The skin is broken up into very 



