Hence we have to rely upon evidences of other kinds. Among these, some which I think dispose absolutely of the fashionable hypothesis while they harmonize with the opposed hypothesis, have now to be named. That their implication should not have been generally recognized would have seemed to me incomprehensible were it not that I have myself only now observed this implication. The facts are these:—
“Verlot mentions a gardener who could distinguish 150 kinds of camellia, when not in flower; and it has been positively asserted that the famous old Dutch florist Voorhelm, who kept above 1,200 varieties of the hyacinth, was hardly ever deceived in knowing each variety by the bulb alone. Hence we must conclude that the bulbs of the hyacinth and the branches and leaves of the camellia, though appearing to an unpractised eye absolutely undistinguishable, yet really differ.” (Darwin, Variation of Animals and Plants, &c., vol. ii, p. 251.)
More recently testimony to like effect has been given by Dr. Maxwell Masters, and has already been quoted by me in a note to [§ 286] in illustration of another truth. He says concerning such variations:—
“To the untrained eye, the primordial differences noted are often very slight; even the botanist, unless his attention be specially directed to the matter, fails to see minute differences which are perceptible enough to the raiser or his workmen.... These apparently trifling morphological differences are often associated with physiological variations which render some varieties, say of wheat, much better enabled to resist mildew and disease generally than others. Some, again, prove to be better adapted for certain soils or for some climates than others; some are less liable to injury from predatory birds than others, and so on.”
In his Vegetable Teratology, p. 493, Dr. Masters names another fact having a like implication—the fact that among seedling stocks which have not yet flowered, those which will produce double flowers are distinguishable. He says:—
“This separation of the single from the double-flowered plants, M. Chatié tells us is not so difficult as might be supposed. The single stocks, he explains, have deep green leaves (glabrous in certain species), rounded at the top, the heart being in the form of a shuttlecock, and the plant stout and thick-set in its general aspect, while the plants yielding double flowers have very long leaves of a light green colour, hairy and curled at the edges, the heart consisting of whitish leaves, curved so that they enclose it completely.”
What is the general truth implied? Clearly that there exists no such thing as an independent local variation. Some marked change in the form or colour of a flower or a fruit draws attention; and, being a change which interests the florist or gardener, pecuniarily or otherwise, not only draws attention but usually monopolizes attention: the natural impression produced being that this variation stands there by itself—is without relation to variations elsewhere. But now it turns out that there are concomitant variations all over the plant. Even in underground bulbs certain appreciable differences go along with certain conspicuous differences in the flowers. And if along with a striking change in a flower which the florist contemplates, there go changes all over the plant not obvious to careless observers but visible to him, we must infer that there are everywhere minute differences which even the florist cannot perceive: the whole constitution of the plant has diverged in some measure from the constitutions of kindred plants. Every local variation implies a change pervading the entire organism, manifested in concomitant variations everywhere else.
If so, what becomes of the hypothesis of determinants—the hypothesis that there is a special element in the germ-plasm which results in a special local modification in the adult organism? That there are no facts supporting it has been all along manifest; but now it is manifest that the facts directly contradict it.
At the same time it may be remarked that while the facts are wholly incongruous with the hypothesis of determinants and its accompanying elaborate speculation, they are not incongruous with the alternative hypothesis. Impossible though it may be to imagine the natures of those ultimate units peculiar to each species, which have proclivities towards the particular form of organization characterizing it, yet that a change of structure arising in one part of the organism is accompanied by multitudinous changes of structure in other parts of the organism, is not only congruous with the belief that there exist such constitutional units, but yields it distinct support. For if, as above argued, a conspicuous local variation is not the result of any modification of units special to the locality, but is the result of a modification of the units at large, then it must happen that such modification must have its effects on all other parts of the organism; so that there cannot fail to result all those small concomitant variations above indicated.
May we not also say that it becomes less incomprehensible that structural changes caused by use and disuse are inherited? If, as we see, a local variation spontaneously arising is accompanied by multitudinous other local variations, implying a necessary correlation between each local variation and the general constitution of the organism; then it may be argued that if a marked change of function in an organ causes increase or decrease of it, this general correlation implies that there must be a reciprocal reaction between the part and the whole, tending to re-establish their congruity. The constitution at large will in so far be changed, and along with its change will go corresponding changes in the sperm-cells and germ-cells.