Vol. X] VON GELDERN—SKIN OF ANOLIS CAROLINENSIS 87 



take on the green state, but after allowing them to rest for a short 

 time, most of them assume the brown state. I have found this to 

 be true in general. Also, if a brown Anolis is taken out of its cage 

 and held in the hand it becomes green in a few minutes. This 

 characteristic change occurs quickly even in animals which have 

 been kept in captivity for a ntunber of weeks and have apparently 

 become tame. 



It is evident that various factors influence color states and the 

 problem becomes even more complex when one considers that 

 certain areas of the skin may be light colored, as in the case of the 

 mid-dorsal stripe, while the rest of the skin may be dark. One 

 must admit that the skin is influenced by three factors, tem- 

 perature, light and emotional or nervous conditions, induced, no 

 doubt, by way of sense organ stimuli. Yet we get opposite effects 

 in two areas of the skin of the same animal. One would hardly 

 expect light and temperature to have a selective action on the skin. 



Structure of the Skin of Anolis 



The chief object of this paper is to present a review of the his- 

 tological structure of the skin of Anolis and to add some observa- 

 tions with the hope that the further investigation of the color 

 changes may be enhanced and some of the factors governing the 

 color states explained. It is not claimed that a knowledge of the 

 minute structures and their relations will offer a full explanation 

 of these changes, but without suclt* a knowledge, physiological 

 experiments must fail to accomplish this end. It is only by keeping 

 in mind the structure of the skin that the actual processes involved 

 may be surmized and physiological data be applied in actual 

 explanation of the problems. 



The skin of Anolis is comparatively thin and loosely attached 

 except at the sides and dorsum of the head and tail. On closer 

 observation it is seen that it is not smooth but is thickly studded 

 with small, closely-packed scales which vary in shape, color, and 

 size in different parts of the body. These small scales, designated 

 as scutes by Carlton, are smooth and shiny. 



The scales situated along the mid-dorsal line are irregular in 

 shape and size with slight tendency toward a hexagonal outline 

 (Fig. i). They are well separated and measure 0.29 mm. length- 

 wise to the body and 0.305 mm. in the transverse direction. A 

 thickened, linear, longitudinal keel may be present in the mid-line 

 of the scale. The scales on the dorso-lateral aspect of the body are 



