274 PROCEEDINGS OF THE AMERICAN ACADEMY. 



as well as in the light, and, as already shown, gives not the least evi- 

 dence of direct stimulation of the melauophores. 



Thus in three fundamental respects the pigment changes in Anolis 

 differ from those in Chameleon, and suggest separate lines of phylo- 

 genetic differentiation, even though all such changes are to be traced 

 back to the responses to light of the simpler form of tegumeutary chro- 

 matophores. 



IV. Summary. 



1. The skin of Anolis carolinensis may be made to assume one or 

 other of two extreme colors, dark-brown and pea-green. 



2. The brown state for animals in confinement is taken on in daylight, 

 and is produced by the outward migration of pigment granules from 

 the bodies of the melauophores into their processes and ultimate branches. 



3. The outward migration is accomplished in about four minutes. 



4. It may be induced either by the mechanical stimulation of the 

 skin or by the action of the sympathetic nerve centres. 



5. The brown state is ordinarilv maintained through a tonus estab- 

 lished by the sympathetic nerves and dependent upon, the stimulation of 

 the nervous end-organs iu the skin of Anolis by light. 



G. The melauophores of Anolis are not stimulated directly by light. 



7. The green state is taken on iu the dark. 



8. It is produced by the iuward migration of the pigment granules of 

 the melauophores, whereby the reflecting ochrophore layer becomes 

 exposed to light. 



9. The inward migration is accomplished in about twenty-five 

 minutes. 



10. It may be induced by any means which brings the melanophores 

 into an unstimulated state: darkness, cessation of circulation, ether 

 narcosis, nicotine poisoning, and possibly the cutting of nerves. 



11. The green state represents the state of rest for the melanophore 

 cells. 



Bibliography. 

 Bert. P. 



'75. Sur le mccanisme et les causes des changements de couleur chez le 

 Cameleon. C. R. Acad. Sci., Paris, torn. 81, pp. 9:38-941. 



Briicke, E. 



'52. Untersuchungen uber den Farbenwechsel des afrikanischen Cha- 

 maleons. Denkschr. kais. Akad. Wiss., Wien. Math.-Naturw. 

 CI., Bd. 4, Abt. 1, pp. 179-210, 1 Taf. 



