Eccentricities of the Animal Creation.

by John Timbs

The Chameleons spend their lives in trees, for clinging to the branches of which their organization is admirably adapted. There they lie in wait for the insects which may come within their reach; and it has been thought that, in such situations, their faculty of changing colour becomes highly important in aiding them to conceal themselves. The powers of abstinence possessed by this singular race are very great; and hence, most probably, arose the old fable of their living on air, which was for a long time considered to be "the Chameleon's dish." One has been known to fast upwards of six weeks without taking any sustenance, though meat-food and insects were procured for it. Notwithstanding this fast, it did not appear to fall away much. It would fix itself by the feet and tail to the bars of the fender, and there remain motionless, enjoying the warmth of the fire for hours together. Hasselquist describes one, that he kept for nearly a month, as climbing up and down the bars of its cage in a very lively manner.

The power of the Chameleon's changing colour long exercised the ingenuity of the old naturalists. Hasselquist thought that the changes of colour depended on a kind of disease, more especially a sort of jaundice, to which the animal was subject, particularly when it was put in a rage. M. D'Obsonville thought that he had discovered the secret in the blood, and that the change of colour depended upon a mixture of blue and yellow, whence the different shades of green were derived; and these colours he obtains from the blood and the blood-vessels. Thus he says that the blood is of a violet hue, and will retain its colour on linen or paper for some minutes if previously steeped in a solution of alum, and that the coats of the vessels are yellow; consequently, he argues, that the mixture of the two will produce green. He further traces the change of colour to the passions of the animal. Thus, when a healthy Chameleon is provoked, the circulation is accelerated, the vessels that are spread over the skin are distended, and a superficial blue-green colour is produced. When, on the contrary, the animal is imprisoned, impoverished, and deprived of free air, the circulation becomes languid, the vessels are not filled, the colour of their coats prevails, and the Chameleon changes to a yellow-green, which lasts during its confinement.

Barrow, in his "Travels in Africa," declares that previously to the Chameleon's assuming a change of colour, it makes a long inspiration, the body swelling out to twice its usual size; and as the inflation subsides, the change of colour gradually takes place, the only permanent marks being two small dark lines passing along the sides. Mr. Wood conceives from this account that the animal is principally indebted for these varied tints to the influence of oxygen. Mr. Spittal also regards these changes as connected with the state of the lungs; and Mr. Houston considers this phenomenon as dependent on the turgescency of the skin. Dr. Weissenborn thinks it not unlikely that the nervous currents may directly co-operate in effecting the changes of colour in the Chameleon.

Mr. H. N. Turner, writing from personal observation of the phenomenon in a live Chameleon in his possession, says:—"It has been generally imagined that the purpose of the singular faculty accorded to the Chameleon is to enable it to accommodate its appearance to that of surrounding objects." Mr. Turner's observations do not, however, favour the idea, but seem rather to negative it. The box in which Mr. Turner's Chameleon was kept was of deal, with glass at the top, and a piece of flannel laid at the bottom, a small branching stick being placed there by way of a perch. He introduced, at various times, pieces of coloured paper, covering the bottom of the box, of blue, yellow, and scarlet, but without the slightest effect upon the appearance of the animal. Considering that these primary colours were not such as it would be likely to be placed in contact with in a state of nature, he next tried a piece of green calico, but equally without result. The animal went through all its usual changes without their being in any way modified by the colour placed underneath it. The general tint approximated, as may be readily observed, to those of the branches of trees, just as those of most animals do to the places in which they dwell; but Mr. Turner did not observe the faculty of changing called into play with any apparent object. It is only when the light is removed that the animal assumes a colour which absorbs but little of it.

Not to go further into the numerous treatises which have been published on this intricate subject without arriving at a just conclusion, we refer to the able and interesting paper of Mr. Milne Edwards, for whose acuteness the solution of this puzzling phenomenon was reserved. The steps by which he first overthrew the received theories on the subject, and then arrived at the cause of the change of colour, is shown in the following results, derived from observing two Chameleons living, and researches after the animals had died, on the structure of their skin, and the parts immediately beneath it.

1. That the change in the colour of the Chameleon does not depend essentially either on the more or less considerable swelling of their bodies, or the changes which might hence result to the condition of their blood or circulation; nor does it depend on the greater or less distance which may exist between the several cutaneous tubercles; although it is not to be denied that these circumstances probably exercise some influence upon the phenomenon.

2. That there exist in the skin of these animals two layers of membranous pigment, placed the one above the other, but disposed in such a way as to appear simultaneously under the cuticle, and sometimes in such a manner that the one may hide the other.

3. That everything remarkable in the changes of colour in the Chameleon may be explained by the appearance of the pigment of the deeper layer to an extent more or less considerable, in the midst of the pigment of the superficial layer, or from its disappearance beneath this layer.

4. That these displacements of the deeper pigment do in reality occur; and it is a probable consequence that the Chameleon's colour changes during life, and may continue to change even after death.

5. That there exists a close analogy between the mechanism by the help of which the change of colour appears to take place in these reptiles, and that which determines the successive appearance and disappearance of coloured spots in the mantles of several of the cephalopods.