AUGUST. 203 



not, it is certain that it now renders the animal quite in- 

 conspicuous. Particularly when it is resting upon a rough- 

 barked tree is this true ; and one of my first objects in 

 studying the species in its native haunts was to determine 

 how far the markings were changeable and under their 

 owner's control. Many specimens were found to be quite 

 dark — indeed, almost black — while others were so light 

 that the undulating transverse bars upon the back were 

 very distinct and discernible at a considerable distance. 

 This difference, I am quite sure, bore no relation to the 

 surroundings; and the specimens subsequently collected 

 and kept under daily observation for nine weeks practi- 

 cally retained the light or dark coloring they possessed at 

 the time of capture. In confinement many individuals 

 remained of a light color under all circumstances ; others, 

 that were dark when received, became light for brief peri- 

 ods, but were very dark fully ninety-five per cent of the 

 time they were under observation. 



The long and broad glistening green markings upon 

 each side of the abdomen are equally variable — certainly 

 not a distinction of sex, as suggested by Le Conte and Say — 

 and often absent for weeks in specimens which occasion- 

 ally exhibited them in all their brilliancy. 



In no instance was there that prompt change of hue 

 that we see in the tree-toad, and even more so in the 

 wood-frog. The change in the latter is as abrupt and 

 complete as in certain fishes, and is particularly significant, 

 inasmuch as it is the only frog that needs protective color- 

 ing, living as it does in woodland tracts, where it is ex- 

 posed to an abundance of enemies ; and may it not be 

 that, by its power to adapt itself to the general color of 

 the surroundings, it renders itself inconspicuous to the 

 insects upon which it preys ? If so, the control over its 

 color becomes doubly advantageous. 



Vision in the pine-tree lizard is apparently not very 



