As to the function of anger and hate, this has already been intimated in the remarks we have just made on its origin and development. For function it is which gives rise to organ and activity; in some unknown, mysterious way the pressing life-struggle for useful mental activity determines ultimately its appearance. We know that extremely hard conditions, which would threaten the continued existence of animate life as a whole, or of any large subdivision, would give rise to new perceptions and emotions by which a saving remnant would escape; and on this principle we must expect the most signal psychic advance of the future at that seemingly remote period when mankind will be threatened with extinction by the slow refrigeration of the earth. A long-continued uniformity of easy conditions of life, as in the tropics, is distinctly unfavourable to psychic progress; but let a glacial period invade that zone, and the changed conditions would awaken such a struggle for existence in all organisms, man included, that new organic and mental types would be developed. The necessities of existence and the self-interest of the individual in an unceasingly sharp competition develop slowly in the few those mental modes which, from their functional importance, become the heritage of a race and _genus_; and these “sports” thereby secure to themselves a certain temporary dominancy. This is the history of life in general, and of man in particular. How demand determines supply, how necessity is the mother of invention, is obvious enough in man, who, clearly conceiving the function, sets about by his knowledge of means to accomplish the needed improvement; but in the lower life, which is incapable of such teleological foresight, we can only say that through pain of lack in the altered conditions of existence there is stimulated a blind, intense struggle, which, moving out in all lines, somewhere, at sometime, by mere chance hitting on the right variation, sticks to it and accomplishes its own salvation, and leaves descendants who tend in the same direction. New psychic qualities, as well as new physical organs, are in some way gradually determined through struggle which is practically blind. That mental variation, that bodily variation, which was incessantly demanded in the struggle of existence does somehow ultimately appear, is, indeed, a fact which, for the present at least, we can only state in this indefinite, unsatisfactory manner. Blind, pain-impelled will, fiercely striking out in every direction, does at length, achieve those new psychical and physical forms which are most needed by life. The chance serviceable variation is fixed and continued by reason of its serviceability; but when its utility wanes by reason of new life factors appearing or new conditions of existence, it is lost by disuse, or survives in rudimentary forms.