Colouration in Animals and Plants

by Alfred Tylor

After showing in detail that the body is made up of an infinite number of units, each of which is a centre of more or less independent action, he proceeds as follows:—

"It is universally admitted that the cells or units of the body increase by self-division or proliferation, retaining the same nature, and that they ultimately become converted into the various tissues of the substances of the body. But besides this means of increase I assume that the units throw off minute granules, which are dispersed throughout the whole system; that these, when supplied with proper nutriment, multiply by self-division, and are ultimately developed into units like those from which they were originally derived. These granules may be called gemmules. They are collected from all parts of the system to constitute the sexual elements, and their development in the next generations forms a new being; but they are likewise capable of transmission in a dormant state to future generations, and may then be developed. Their development depends on their union with other partially developed or nascent cells, which precede them in the regular course of growth.... Gemmules are supposed to be thrown off by every unit; not only during the adult state, but during each stage of development of every organ; but not necessarily during the continued existence of the same unit. Lastly, I assume that the gemmules in their dormant state have a mutual affinity for each other, leading to their aggregation into buds, or into the sexual elements. Hence, it is not the reproductive organs or buds which generate new organisms, but the units of which each individual is composed." [6]

Now, suppose that instead of these hypothetic gemmules we endow the units with memory in ever so slight a degree, how simple the explanation of all these facts becomes! What an unit has learned to do under given conditions it can do again under like circumstances. Memory does pass from one unit to another, or we could not remember anything as men that happened in childhood, for we are not physically composed of the same materials. It is not at all necessary that an unit should remember it remembers any more than we in reading are conscious of the efforts we underwent in learning our letters. Few of us can remember learning to walk, and none of us recollect learning to talk. Yet surely the fact that we do read, and walk, and talk, proves that we have not forgotten how.

Bearing in mind, then, the fundamental laws that the offspring is one in continuity with its parents, and that memory arises chiefly from repetition in a definite order (for we cannot readily reverse the process—we cannot sing the National Anthem backwards), it is easy to see how the oft-performed actions of an individual become its unconscious habits, and these by inheritance become the instincts and unconscious actions of the species. Experience and memory are thus the key-note to the origin of species.

Granting that all living matter possesses memory, we must admit that all actions are at first conscious in a certain degree, and in the "sense of need" we have the great stimulation to action.

In Natural Selection, as expounded by Mr. Darwin, there is no principle by which small variations can be accumulated. Take any form, and let it vary in all directions. We may represent the original form by a spot, and the variations by a ring of dots. Each one of these dots may vary in all directions, and so other rings of dots must be made, and so on, the result not being development along a certain line, but an infinity of interlacing curves. The tree of life is not like this. It branches ever outwards and onwards. The eyes of the Argus pheasant and peacock have been formed by the accumulation, through long generations, of more and more perfect forms; the mechanism of the eye and hand has arisen by the gradual accumulation of more and more perfect forms, and these processes have been continued along definite lines.

If we grant memory we eliminate this hap-hazard natural selection. We see how a being that has once begun to perform a certain action will soon perform it automatically, and when its habits are confirmed its descendants will more readily work in this direction than any other, and so specialisation may arise.

To take the cases of protective resemblance and mimicry. Darwin and Wallace have to start with a form something like the body mimicked, without giving any idea as to how that resemblance could arise. But with this key of memory we can open nature's treasure house much more fully. Look, for instance, at nocturnal insects; and one need not go further than the beetles (Blatta) in the kitchen, to see that they have a sense of need, and use it. Suddenly turn up the gas, and see the hurried scamper of the alarmed crowd. They are perfectly aware that danger is at hand. Equally well do they feel that safety lies in concealment; and while all the foraging party on the white floor are scuttling away into dark corners, the fortunate dweller on the hearth stands motionless beneath the shadow of the fire-irons; a picture of keen, intense excitement, with antennæ quivering with alertness. On the clean floor a careless girl has dropped a piece of flat coal, and on it beetles stand rigidly. They are as conscious as we are that the shadow, and the colour of the coal afford concealment, and we cannot doubt that they have become black from their sense of the protection they thus enjoy. They do not say, as Tom, the Water Baby, says, "I must be clean," but they know they must be black, and black they are.

There is, then, clearly an effort to assimilate in hue to their surroundings, and the whole question is comparatively clear.

Mr. Wallace, in commenting upon the butterfly (Papilio nireus)—which, at the Cape, in its chrysalis state, copies the bright hues of the vegetation upon which it passes its dormant phase—says that this is a kind of natural colour photography; thus reducing the action to a mere physical one. We might as well say the dun coat of the sportsman among the brown heather was acquired mechanically. Moreover, Wallace distinctly shows that when the larvæ are made to pupate on unnatural colours, like sky-blue or vermilion, the pupæ do not mimic the colour. There is no reason why "natural photography" should not copy this as well as the greens, and browns, and yellows. But how easy the explanation becomes when memory, the sense of need, and Butler's little "dose of reason," are admitted! For ages the butterfly has been acquainted with greens, and browns, and yellows, they are every day experiences; but it has no acquaintance with aniline dyes, and therefore cannot copy them.