Its action, of course, is, and must be, destructive and negative. The evolution of a new species is as necessarily a process which is constructive and positive, and, as all must admit, is one due to those variations upon which natural selection acts. Variation, which thus lies at the origin of every new species, is (as we have seen) the reaction of the nature of the varying animal upon all the multitudinous agencies which environ it. Thus “the nature of the animal” must be taken as the cause, “the environment” being the stimulus which sets that cause in action, and “natural selection” the agency which restrains it within the bounds of physiological propriety. We may compare the production of a new species to the production of a statue. We have (1) the marble material responding to the matter of the organism; (2) the intelligent active force of the sculptor, directing his arm, responding to the psychic nature of the organism, which reacts according to law as surely as in the case of reflex action in healing, or in any other vital action; (3) the various conceptions of the artist, which stimulate him to model, responding to the environing agencies which evoke variation; and (4) the blows of the smiting chisel, corresponding to the action of natural selection. No one would call the mere blows of the chisel—apart from both the active force of the artist and the ideal conceptions which direct that force—_the_ cause of the production of the statue. They are _a_ cause—they help to produce it and are absolutely necessary for its production. They are a _material_ cause, but not the _primary_ cause. This distinction runs through all spheres of activity. Thus the inadequacy of “natural selection” to explain the origin of species runs parallel with its inadequacy to explain the origin of instinct, as before pointed out. The _formal_ discoverer of a new fossil is the naturalist who first sees it with an instructed eye, appreciates and describes it, not the laborer who accidentally uncovers but ignores it, and who cannot be accounted to be, any more than the spade he handles, other than a mere _material_ cause of its discovery. So we must regard the sum of the destructive agencies of nature, as a material cause of the origin of new species, their formal cause being the reaction of the nature of their parent organisms upon the sum of the multitudinous influences of their environment. This kind of action of “the organism”—this formal cause—has been compared by Mr. Alfred Wallace, and by me, with the action of the organism in its embryonic development; and this, I have further urged, is to be likened to the processes of repair and reproduction of parts of the individual after injury, and this, again, to reflex action, and, finally, this last to instinct as manifested in ourselves and in other animals also.