BEHAVIOR AND COLOR CHANGES OF TREE FROGS 69 



kunstlichen Blattern unci es beweist dieser Umstand allein 

 schon, dass als auslosender Reiz wohl nur gewisse Beriihrungs- 

 empfindungen in Betracht kommen." (p. 506). 



It will be noticed that this experiment was conducted in 

 darkness, thus excluding the influence of either light or vision. 

 By two other forms of experiment he claimed to demonstrate 

 that by contact with a rough surface a darkening of the skin 

 was produced, even to complete blackening. So simple seemed 

 the experiments that no time was spared in putting them to the 

 test. Accordingly I sought to duplicate the experiments, and 

 placed the same number of frogs in the wire cage, the bottom 

 of which was covered with a very coarse jute matting, and in 

 the glass jar. After several hours under these conditions the 

 only difference appreciable was that the color of most of those 

 in the jar was definitely darker than those in the cage ; just the 

 rever.se of what should have been the case. To vary the ex- 

 periment a glass jar was prepared by enclosing a coarse wire 

 netting over the sides, and coarse blotting paper over the bottom. 

 Into this several specimens were placed and left for several 

 hours, but all the while under critical observation. It was not 

 possible to distinguish the slightest indication of color change. 

 The jar was then placed under a black hood and again left for 

 an hour. In one or two cases there seemed to be a slight darken- 

 ing of the green, but it was not marked. The question of the 

 influence of darkness will be considered in another section. 



I next tried the experiment with leaves. Several of the 

 darkest specimens were placed in a jar in which had been ar- 

 ranged a leafy branch and leaves scattered over the bottom. 

 Two at once took up a position on the leaves, two clung to the 

 sides of the jar, and one remained on the bottom. They were 

 watched critically for two hours, but with only negative re- 

 sults, no change of color occurring. Next the experiment 

 was tried of putting a jar of these specimens in a cool, dark 

 room over night and early the following morning introducing 

 into the jar a leafy branch and leaving in the dark for some 

 hours. As before, the result was wholly negative. The ex- 

 periment was varied by using the wire cage and a smooth glass 

 jar each with the same number of specimens and leaving both 

 in the same conditions of light and temperature during an 

 entire forenoon. At the end it was found that in each case 



