COLOR CHANGES IX SKIN OF LIZARD. 449 



I have made no experiments as to the length of time these 

 lizards require for a complete change of color. Anyhow it takes 

 less than a quarter of an hour. The photographs have been 

 mark- with Ilford I '.Dichromatic Plates, which were each exposed 

 during one and a half minutes. The animals remained during 

 thi^ comparatively long time almost immobile on the same spot. 

 The pl.itt : in the same liquid during quite the 



-.tine time. They h.i\e not at all been retouched or altered in 

 .my \\.ty. The p"-iti\t - are made with gaslight paper, those of 

 . i .md 2 an d i"nr quite the same time and have after- 



ward- been worked out into a cliche together. Therefore these 

 ligir reliable data for a comparison of the color of the 



-kin of the -ame .mim.il on a white background with free and 

 \\ith covered I'!:- te< hnical peculiarities given above are 



mentioned to pn>\e that the two figures give accurate data for 

 the di: f tin- color under these different circumstan 



,} c.m only le-- directly be compared with the others, but it 

 shows cle.uK enough th.it on a black background the color of 

 the -kin i- ot .in aln . en shade. The plate of this figure h.i- 



d l"i the -ame lime as those of Figs. I and J, but 

 o\\in^ to the black bai k^round it is more or less underexposed. 

 Theieton- the animal appears brighter than it was in reality. 



The external inlluem es in these experiments were alnio-t 

 quite constant. I -tndied the color changes of Ptychozoon al\\a\ - 

 on quite the Ban ' in diffuse daylight at a distance of circa 



i in. tiom the window. The intensity of the light was al\\a\- 

 pi.uticalK the -ame. the time being the dry monsoon, \\hen 

 bet\\een s and u A.M. the intensity of the light in the tropics 

 i- quite equal. The difference in maximum and minimum of the 

 it there was any difference at all) was very slight 

 and al-o the of humidity did not van" noticeably during 



the experiments. The structure of the substratum was in all 

 experiment- the .-ame. This, however, pro\ ed to be of little 

 importance as was >hown by a little minor experiment. Once 

 I tried the same experiments by bringing the animals succes-i\ cly 

 on white paper and on black velvet, but the color change- v 

 the same as in the experiments with the animals in differently 

 clad glass-vessels. 



From the abo\ e -tated peculiarities \\e may conclude that 



