I do not, however, assert that _every_ species is liable to be interfered with _ab extra_; that is a question which the greater or less susceptibility of the several races, as originally constituted, can alone decide; still less would I willingly lend a helping hand to that most mischievous of dogmas, that they are _all_-important in their operation,--or, in other words, that they possess within themselves the inherent power (though it may not invariably be exercised) of shaping out (provided a sufficient time be granted them, and in conjunction with the advancing requirements of the creatures themselves) those permanent organic states to which the name of species (in a true sense) is now applied. Such a doctrine is in reality nothing more than the transmutation theory, in all its unvarnished fulness; and I do not see how it can be for a moment maintained, so long as facts (and not reasoning only) are to be the basis of our speculations. I repeat, that it is merely _within fixed specific bounds_ that I would advocate a freedom of development, in obedience to influences from without: only I would widen those limits to a much greater extent than has been ordinarily done,--so as to let in the controlling principle of physical agents, as a significant adjunct for our contemplation. It does indeed appear strange that naturalists, who have combined great synthetic qualities with a profound knowledge of minutiae and detail, should ever have upheld so monstrous a doctrine as that of the transmission of one species into another,--a doctrine, however, which arises almost spontaneously,--if we are to assume that there exists in every race the tendency to _an unlimited progressive improvement_. There are certainly no observations on record which would, in the smallest degree, countenance such an hypothesis. Many animals and plants, it is true, are capable of considerable modifications and changes, for the better,--very much more than is the case with others. But what does this prove, except that their capacity for advancement has a slightly wider compass than that of their allies? It touches not the fact, that the boundaries of their respective ranges are absolutely and critically defined. It is moreover a singular phaenomenon, and one in which the strongest proofs of design (or a primary adjustment of limits with a view to the future) may be discerned, that the members of the organic creation which display the greatest adaptive powers, are those which were apparently destined to become peculiarly attendant upon man. "The best-authenticated examples," says Sir Charles Lyell, "of the extent to which species can be made to vary may be looked for in the history of domesticated animals and cultivated plants. It usually happens that those species which have the greatest pliability of organization, those which are most capable of accommodating themselves to a great variety of new circumstances, are most serviceable to man. These only can be carried