Page:Popular Science Monthly Volume 34.djvu/177

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individuals remained of a light color under all circumstances; others, that were dark when received, became light for brief periods, 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 occasionally exhibited them in all their brilliancy.

In no instance was there that prompt change of hue that we see in the tree-toad (Hyla versicolor), and even more so in the wood-frog (Rana sylvatica). 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 coloring, living as it does in woodland tracts, where it is exposed 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 acute, although the eyes are exceedingly bright, and, when coupled with certain movements of the head, suggest considerable intelligence. It was found very difficult to test their visual powers, although, once captured, these lizards became extremely tame, patient, and obedient, and I could only infer that the sense of sight was none of the best from the fact that when held to a mosquito-frame in a window, upon which house-flies were walking, they missed fully one half of those at which they snapped; and other lizards in confinement, but where every possible freedom of movement was practicable, often made many attempts to capture flies before success crowned their efforts. If, therefore, when at large, they depended principally upon winged insects for subsistence, their lives would indeed be laborious ones; but insects of sluggish movements, ants, and small spiders, are all freely partaken of. My friend Mr. George Pine, of Trenton, N. J., a very careful observer, assures me that of the two insects, house-flies and Croton-bugs, his lizards certainly preferred the latter, but were not particularly expert in capturing them. And now, assuming that the eye-sight of these little reptiles is not highly developed, what of the curious "pineal eye" which they possess? Prof. Macloskie has recently announced in "Science" that it "is so well developed ... that it may probably seem to warn its owner of the advent of daylight. It is a lenticular, glassy area of the skin of the vertex (about a millimetre in sagittal diameter), surrounded by a yellow border, and having a dark spot in its center. The dark spot is opaque, caused by a mass of pigment internal to the