BEHAVIOR AND COLOR CHANGES OF TREE FROGS 61 



this inference was perhaps incorrectly attributable to the sole 

 effect of light intensity. 



To test the effects of direct sunlight the cages were taken 

 from the diffuse light and placed on the table in direct sun. As 

 a rule this had the effect of a rapid lightening of the skin, and 

 the gradual fading of the pigment patterns of both legs and 

 back. One of the specimens in this case rapidly assumed a 

 green color in the light of the sun, while the other became 

 whitish-grey. This experiment was made at nine o'clock and 

 at two o'clock the green color persisted in the one, while the 

 other specimen had become very dark, even darker than at the 

 time of the test. 



This experiment with direct sun was repeated many times 

 in the course of the following few days, and usually with the 

 same result, viz., the rapid lightening of coloration. It must 

 be stated, however, that the green color was exceptional, and 

 when it occurred was more persistent. In one case to be noticed 

 later this green color became singularly permanent under a 

 wide range of experiments, continuing over several days. 



The next experiment consisted of putting one cage under a 

 black hood, while the other was left as a control in the diffuse 

 light of the room. After an hour the hood was removed but 

 not the slightest change of color had taken place. Like the 

 preceding experiment, this was repeated many times but with 

 almost uniformly negative results. This seems in rather marked 

 contrast with that associated with the capture of specimens 

 and their transfer in the dark collecting box to the laboratory, in 

 which the very opposite was usual, viz., the darkening of the 

 skin. This also will be further considered in a later connection. 



Two further experiments along this line are rather important. 

 First may be mentioned the specimen taken in early spring, 

 referred to in an earlier connection. This specimen when taken 

 was of the usual whitish grey color. It was carried home from 

 the woods and kept in an open jar on a back porch free from 

 interruption. Experiments as to its light reaction seemed very 

 prompt and more than usually positive. In a bright diffuse 

 light it rapidly became light in color. Placed under a very 

 dark hood for half an hour it had resumed the dark slaty color. 

 The' hood being removed a rapid lightening of the skin was 

 very evident. The experiment was repeated several times and 



