190 REPTILES OF THE WORLD 



however, many lizards with large, coarse scales, either 

 smooth or keeled, that momentarily vary in hue. 

 Usually, the variation among such examples consists 

 of the intensification of a regular and permanent pat- 

 tern, or the fading of this; as a good illustration we 

 may take the Common Swift, Sceloporus undulatus, of 

 the United States, and the allies of that reptile among 

 which patches of pale gray on the abdomen and throat 

 will assume really startling shades of blue and green, 

 while the pattern on the creature's back varies from 

 shades of gray into brown or yellow. Among the mem- 

 bers of the Chamceleontidce there are not only marked 

 changes of the body hue, but strange patterns come 

 and go. 



Numerous experiments have been conducted in the 

 Reptile House of the New York Zoological Park. Fol- 

 lowing is a partial list of these, the same relating to 

 Chamceleon vulgaris: 



Specimen A. Placed in the sunlight so that but one side of the lizard 



was exposed to the rays. 

 Specimen B. Placed in the sunlight at an angle to entirely suffuse the 



reptile with the rays. 

 Specimen C. Placed in a dark box — Temperature 75° Fahrenheit. 

 Specimen D. Placed in a dark box — Temperature 50° Fahrenheit. 



After fifteen minutes these results were noted: 



Specimen A. Was a dark brown on the side that had been exposed to 



the sun; the shadowed side was a pale brown, mottled 



with green. 

 Specimen B. A uniform brown, deeper than the dark side of Spec. A. 

 Specimen C. When the cover of the box was drawn the lizard emerged 



in a brilliant coat of green. 

 Specimen D. Crawled sluggishly from its cold quarters. Its color was 



a uniform, slaty gray. 



Repetition of these experiments produced similar re- 

 sults, showing light and temperature to be among the 

 factors responsible in changing the lizards' hues. 



Another test was along lines to ascertain if the lizards 



