the more there may exist between them that equality of vitality which is merely the negation of competition. This explains why we oftener remark equal vitality between different species than between varieties of the same species. Certain species even suggest each other, and have mutual need each of the other for their existence. If, for instance, the quantity of vegetables, or of certain animal species which we require for our nourishment, were to decrease, it would necessarily follow that population would diminish proportionately; but that diminution would allow the other species to resume their former development; therefore the equilibrium is maintained of necessity.
As to the possibility of morphological alterations, by the accumulation of individual modifications, Hartmann himself admits that Darwin has cited more than one instance of it, and a marked one in the skeleton of pigeons: he objects, it is true, that there was some aid from art in these different cases. Very true! but that proves that analogous changes are at least possible through natural selection. Hartmann adds, that a pair of teeth, or vertebræ, or fingers, more or less, or a vertebra shaped in such or such a way, are exactly the marks by which zoologists oftenest distinguish species, and yet he says such marks are of no importance in the struggle for life. This seems to us an oversight; for they are precisely those scarcely appreciable modifications which have the greatest importance from the point of view of selection and competition.
Darwin and Hartmann stand at the opposite poles of modern thought. To Darwin belongs the most fertile idea of the age, an idea which upsets all the ancient ways of conceiving the world, and includes the first natural explanation yet given of order, of organization, and of intelligence itself. Hartmann, on the contrary, takes us back to the ancient labyrinths of teleology; between two explanations, one natural and the other supernatural, we have always found him, thus far, pronouncing for the latter. We detect a new instance of this predilection in his way of regarding instinct. Darwinism explains it admirably as an hereditary habit resulting from natural selection; a habit can only become formed and inveterate on condition of its aiming at a result useful for the preservation of the individual and the species; that which is not useful cannot become habitual, or at least not hereditary. Vices can be only individual accidents, or else the race is tending toward extinction; all that flows from the force of things, and there is no call for the supposition that the utility of fact grown into habit must have been foreseen, and willed by a supernatural being. But Hartmann prefers to define instinct as "the conscious will (choice) of a means in view of an end unconsciously willed;" and this he does to raise a necessity for the supposition of an intelligent principle, distinct from conscious intelligence, in the bosom of which he may lodge the seat of these unconscious volitions.
Hartmann's love of the supernatural goes so far as to make him