1 66 CHARLES G. ROGERS. 



and this also tended to become permanent as the age of the ani- 

 mals became greater. 



Flamming l observed that the conditions of light as well as of 

 temperature make their impress upon the coloration of the sala- 

 mander. Animals left in dark aquaria become and remain dark, 

 while those in the light, for example, in white porcelain dishes, 

 become light, the temperature of the water being the same in the 

 two cases. 



The recent work of Carlton 2 upon the chameleon Anolis gives 

 us even more striking evidence of the part played by external 

 conditions in the coloration of animals. He found that the skin 

 of Anolis can be made to assume one of two colors, dark brown 

 or pea green. 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 melanopores into the 

 processes and ultimate branches. This outward migration is 

 accomplished in about four minutes. It may be brought about 

 either by mechanical stimulation of the skin or by an act of 

 the nervous system. The brown state is ordinarily maintained 

 by a tonus established by the sympathetic nerves and dependent 

 upon the stimulation of the nervous end organs in the skin by 

 the light. The melanophores of Anolis are not directly stimu- 

 lated by the light. The green state is taken on in the dark, and 

 is produced by the inward migration of the pigment granules of 

 the melanophores whereby the reflecting ochrophore becomes ex- 

 posed to the light. This inward migration requires about twenty- 

 five minutes. It may be induced by any means which will bring 

 the melanophores into the unstimulated state. 



EXPERIMENTS UPON DIEMYCTYLUS. 



The material upon which these observations were made was 

 the salamander Dicmyctylus viridescens. Specimens were collected 

 n the fall of the year and had been kept in the laboratory during 

 the winter in glass jars. The water in the jars was frequently 

 changed and the animals were fed upon raw beef at regular inter- 

 vals. In the spring observations were also made upon specimens 

 just taken from their usual environment with similar results. 



1 Flemming, Arch. f. Mikr. Anat., XLVIII., pp. 690-692. 



2 Carlton, Proc. Atner. Acad. Arts and Sci., XXXIX., No. IO, pp. 259-276. 



