PRIMATES.] MAMMALIA 445 and the small size of the canine teeth are perhaps the most marked and easily defined distinctions that can be drawn between the two groups. Man is universally admitted to form a single genus, Homo of Linnaeus, but a question of considerable import ance in treating of him from a zoological point of view, and one which has been a subject of much controversy, is whether all men should be considered as belonging to one or to several species. This question is perhaps of less importance now than formerly, when those who maintained a plurality of species associated with the hypothesis plurality of origin. One of the strongest arguments against the view that the various races of Man represent more than one species is that none of those who have maintained it have been able to agree as to how many dis tinct specific modifications can be defined, almost .every number from three to twenty or more having been advo cated by different authors. If the distinguishing characters of the so-called species had been so marked, there could not be such a remarkable diversity of opinion upon them. Again, the two facts (1) that, however different the ex tremes of any two races may be in appearance (and it must be admitted that, as advocated by many polygenists, the differences are greater than many which are considered specific among other animals), every intermediate grad ation can be found through which the one passes into the other, and (2) that all races are fertile inter se are quite conclusive in favour of considering Man as repre senting a single species in the ordinary sense in which the word is now used, and of treating of all his various modifications as varieties or races. The great problem at the root of all zoology, the discovery of a natural classification which shall be an expression of our knowledge of the real relationship or consanguinity of different forms, is also applicable to the study of the races of Man. When we can satisfactorily prove that any two of the known groups of mankind are descended from the same common stock, a point is gained. The more such points we have acquired the more nearly shall we be able to picture to ourselves, not only the present, but the past distribution of the races of Man upon the earth, and the mode and order in which they have been derived from one another. But the difficulties in the way of applying zoological principles to the classification of Man are vastly greater than in the case of most animals. When groups of animals become so far differentiated from each other as to represent separate species, they remain isolated ; they may break up into further subdivisions in fact, it is only by further subdivision that new species can be formed ; but it is of the very essence of species, as now universally understood by naturalists, that they cannot recombine, and so give rise to new forms. With the varieties of Man it is otherwise. They have never so far separated as to answer to the physiological definition of species. All races, as said above, are fertile with one another, though perhaps in different degrees. Hence new varieties have constantly been formed, not only by the segmentation of portions of one of the old stocks, but also by various combinations of those already established. Without entering into the difficult question of the method of Man s first appearance upon the world, we must assume for it vast antiquity, at all events as measured by any historical standard. Of this there is now ample proof. During the long time he existed in a savage state a time compared to which the dawn of our historical period is as yesterday he was influenced by the operation of those natural laws which have produced the variations seen in other regions of organic nature. The first Men may very probably have been all alike ; but, when spread over the face of the earth, and become subject to all kinds of diverse external conditions, climate, food, competition with members of his own species or with wild animals, racial differences began slowly to be developed through the potency of various kinds of selection acting upon the slight variations which appeared in individuals in obedience to the tendency planted in all living things. These differences manifested themselves externally in the colour of the skin, the colour, quality, and distribution of the hair, the form of the head and features, and the pro portions of the limbs, as well as in the general stature. Geographical position must have been one of the main elements in determining the formation and permanence of races. Groups of Men isolated from their fellows for long periods, such as those living on small islands, to which their ancestors may have been accidentally drifted, would naturally, in course of time, develop a new type of features, of skull, of complexion, or hair. A slight set in one direc tion, in any of these characters, would constantly tend to intensify itself, and so new races would be formed. In the same way, different intellectual or moral qualities would be gradually developed or transmitted in different groups of Men. The longer a race thus formed remained isolated, the more strongly impressed and the more perma nent would its characteristics become, and less liable to be changed or lost* when the surrounding circumstances were altered, or under a moderate amount of intermixture from other races the more " true " in fact, would it be. On the other hand, on large continental tracts, where no mountain ranges or other natural barriers form obstacles to free intercourse between tribe and tribe, there would always be a tendency towards uniformity, from the amalgamation of races brought into close relation by war or by com merce. Smaller or feebler races would be destroyed or absorbed by others impelled by superabundant population or other causes to spread beyond their original limits ; or sometimes the conquering race would itself disappear by absorption into the conquered. Thus, for untold ages, the history of Man has presented a shifting, kaleidoscopic scene : new races gradually be coming differentiated out of the old elements, and, after dwelling a while upon the earth, either becoming suddenly annihilated or gradually merged into new combinations ; a constant destruction and reconstruction ; a constant tendency to separation and differentiation, and a tendency to combine again into a common uniformity the two tendencies acting against and modifying each other. The history of these processes in former times, except in so far as they may be inferred from the present state of things, is a difficult study, owing to the scarcity of evidence. If we had any approach to a complete palaeontological record, the history of Man could be reconstructed ; but nothing of the kind is forthcoming. Evidence of the anatomical characters of Man, as he lived on the earth during the time when the most striking racial characteristics were being developed, during the long ante-historic period in which the Negro, the Mongolian, and the Caucasian were being gradually fashioned into their respective types, is entirely wanting, or if any exists it is at present safely buried iu the earth, perhaps to be revealed at some unexpected time and in some unforeseen manner. Even the materials from which a history of the modifications of the human species as known to our generation must be constructed are rapidly passing away, as the age in which we live is an age in which, in a far greater degree than any previous one, the destruction of races, both by annihilation and absorption, is going on. Owing to the rapid extension of maritime discovery and commerce, changes such as have never been witnessed before are now taking place in tlie ethnology of the world, changes especially affecting the island popula
tions among which, more than elsewhere, the solution of