72 CHARLES W. HARGITT 



cases the test was made by using a dark hood which could be 

 easily slipped over the jar rendering the interior very dark. 

 Of course, all degrees of time enable one to be certain that a 

 given condition had not been overlooked or escaped attention. 

 Another method, already referred to, was to place the jars or 

 cage in a cool dark room for any desired time. Here one could 

 inspect the results after an hour, or after any number of hours. 

 The results from both methods were to the same effect, viz., 

 that darkness of itself, at least in my experiments, has no appre- 

 ciable effect as to color changes in this species. 



One of the very significant features of all these experiments 

 was the marked discrepancies in results. For example, in one 

 case a specimen w r as transferred from a dark jar into direct 

 sunlight. During the first 15 minutes no color change was 

 apparent; the specimen became very restless, moving about 

 constantly, and soon the color began to darken, and in 15 

 minutes more had become almost black. This is but one of 

 several such cases. 



Temperature. It has been concluded from many observations 

 that temperature is often a feature of marked importance. 

 Parker has so held in relation to Anolis and Phrynosoma (op. 

 cit.), and others likewise have drawn similar conclusions. As 

 shown in experiments with H. versicolor, so with H. arborea, 

 this factor seems not to be of large value in relation to color 

 changes. My experiments with the latter species on this point 

 were made by two modes, viz., first by subjecting the specimen 

 to room temperatures of different degrees; second, by subject- 

 ing specimens to baths of different degrees. Both these were 

 used with this species, but the latter was by far the more con- 

 vincing. By this mode water of measured temperature was 

 prepared and a specimen placed in it for certain definite time. 

 In the first of these temperature tests some five specimens 

 were tried. Four of these showed very evident lightening of 

 color when subjected to a temperature of 30 to 35 degrees C. 

 for 10 minutes. But a fifth specimen grew positively darker 

 under the test and at 36 C. had become almost black. To make 

 it perfectly sure that these results were not due to the water 

 alone others were tested in a warm oven of the same tempera- 

 ture, and with essentially the same results. This curious effect 

 may be noted, that there was marked individual difference as 



