400 M. P. tie Grijs on the Faculty of 



which they rest. The change of C">lour of tlie species of 

 Anolis undoubtedly serves these animals in the first place 

 for protection. That the change of colour in Anolis is partly 

 spontaneous I was able to determine with certainty from 

 specimens that I kept in captivity ; for so long as I kept 

 various examples of A. principalis in a vivarium destitute of 

 plants it was only rarely and only under the influence of 

 sunshine that the animals assume 1 the splendid green colour. 

 Since, however, I have allowed the lizards to run about 

 freely in a glazed verandah full of plants they are almost con- 

 tinually green, and this even when the sky is overcast. Tiie 

 change of colour in the chameleon also serves the almost 

 helpless animal preeminently for protection, for, as a Spanish 

 proverb has it, " a chamasleon seen is a chameleon lost " ! 

 It is an interesting fact that the power of changing colour in 

 Chamaleon vulgaris has apparently adapted itself to the 

 localities whence the specimens are obtained. Examples 

 from places poor in vegetation are unable to produce the 

 beautiful blue-green tints which are assumed by those coming 

 from districts in which plants abound. Some years ago I 

 received some extremely vividly coloured specimens of this 

 kind which I was at first inclined to regard as belonging to 

 a distinct species. I was not told where they had been found, 

 and no such specimens have since come under my notice. 



The coloration of Iguana tuhercalata is also protective. It 

 is true that in this species it is only variations from liglit and 

 dark green that are possible; markings consisting of spots 

 may either appear or disappear. The change of colour in 

 Iguana seems to be more pronounced in young than in old 

 animals; yet I have not sufficient experience as to this, since 

 it was only quite a young individual that I was able to observe 

 more closely. 



That some species spontaneously utilize their power of 

 changing colour in order to absorb or to ward oif iieat is 

 perhaps of more subordinate importance. It is probably a 

 matter of general knowledge that in cool weather Chamcdeon 

 vulgaris becomes almost black on the side on which the 

 sun's rays fall. If the same species be exposed to great heat 

 it becomes bright yellow. A specimen of Amphiholurus 

 barbatus that I have been keeping for a long time turns a 

 perfectly dark colour in tiie morning, when the tiist rays of 

 the sun fall into its cage; at midday it is pale grey, and with 

 continuous sunshine the head is almost white. Most of the 

 Agamidae and Iguanidge, which inhabit the deserts and 

 steppes, become paler under great heat. 



Of much greater importance, on the otiier hand, is the 



