. Journal of experimental zoology. it an object of study. Preliminary trials made at my suggestion by Mr. A. S. Pearseshowed that horned toads obtained from dealers were not usuallyin a very satisfactory condition for work of this kind, and furtherthat the color changes, though present in Phrynosoma, were not Influence of Light and Heat on Melanophores 403 of a very pronounced type. The subject was, therefore, aban-doned till through the kindness of Miss S. R. Armington I cameinto the possession of a large vigorous specimen of Phrynosomablainvillei Gray, from San Diego, California. This specim
. Journal of experimental zoology. it an object of study. Preliminary trials made at my suggestion by Mr. A. S. Pearseshowed that horned toads obtained from dealers were not usuallyin a very satisfactory condition for work of this kind, and furtherthat the color changes, though present in Phrynosoma, were not Influence of Light and Heat on Melanophores 403 of a very pronounced type. The subject was, therefore, aban-doned till through the kindness of Miss S. R. Armington I cameinto the possession of a large vigorous specimen of Phrynosomablainvillei Gray, from San Diego, California. This specimenhad been well fed, had recently shed its skin, and showed in aclear and unmistakable way a series of color changes that hadbeen only faintly indicated in other specimens. The resultsrecorded in this paper refer in the main to the reactions of thisone specimen, though they have been checked by observations onother horned toads in the laboratory. I am under obligationto Miss Armington for the privilege of working with this Fig. I. Dorsal view of Phrynosoma blainvillei, showing the dark coloration due to exposure to day-light. XI- Since both light and heat influence the migration of the pigmentin the melanophores of lizards, it was obvious that in experi-menting on Phrynosoma, both factors were to be kept in a room at 19° C, after an exposure for several hours to brightbut diffuse daylight, the horned toad w^as deep brownish, mottledwith black and white (Fig. i). The head w^as brownish the middle of the back from the head to the tail ran abroad brownish streak, which was much lighter on the neck thanelsewhere. Right and left of this lighter portion and coveringmost of the neck were two large patches almost black in trunk was marked by four chestnut-brown transverse bands 404 G. H. Parker alternating with darker bands. The most anterior of the brownbands was immediately behind the neck and crossed the trunkfrom foreleg to foreleg. The most post
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