one hand by animals and on the other by human groups, we shall arrive at similar results. Without, however, entering into details it will be sufficient to mention the greyhound and the beagle.

V. One of the most singular external characters, and one which has often been insisted upon as being necessarily a character of species, is that presented by the Bosjesman women. It is generally known that at the lower extremity of the loins they develop a fatty mass which sometimes increases to a considerable protuberance, as may be seen in the Hottentot Venus, the model of which is in the Paris Museum. This steatopygia reappears however in certain tribes situated much further north than the Houzouana races, while Livingstone states that certain women of the Boors, incontestably of Dutch origin, had begun to be affected by it. From this fact alone, this exaggerated development of the adipose tissue loses the value which many wished to attach to it.

If, however, the steatopygia were to exist only among the Houzouanas we could not, on that account, regard it as a character of species, for it has been proved in animals where it is only a character of race. Pallas has proved this fact in certain sheep of Central Asia. In these animals the tail disappears and is reduced to a simple coccyx, to the right and left of which are situated two hemispherical fatty masses weighing from twenty to thirty pounds each. Here, again, the variation is proportionally greater than in the Bosjesman

woman.

We cannot regard these sheep as a different species, for when the Russians removed the same animals from the country in which they were born, the steatopygia disappeared in a few generations. It is, therefore, merely a character of race which can only be preserved in the place where it was developed, as may be seen in a number of other cases.

VI. It is evident that the preceding character is just as much internal as external; it is also evident that neither the size, nor the proportions of the trunk and limbs, can vary,

unless the skeleton and the accompanying muscles experience corresponding modifications. The anatomical characters change then with the race in animals, as well as external characters. There are, however, certain facts which relate more directly to anatomy. I will quote a few cases.

A dog's fore-paw possesses normally five well-formed toes, while the hind-paws have only four with a rudimentary fifth. This latter disappears in some races, mostly of a diminutive size. In certain large races, on the contrary, it is developed, and becomes equal to the other four. There must be then a formation of bone corresponding to the tarsus and metatarsus.

Something analogous to the appearance we have just remarked may be observed in the pig, complicated, however, by a fresh phenomenon. Here the normal foot bears two small rudimentary lateral toes, and two medial toes, each with its own hoof. Now in certain races, already known to the ancients, a third medial toe is developed, and the whole is enveloped in a single hoof. Instead of being cloven-footed, which is the normal type of the species, the race becomes solidungulate.

Nothing of this kind is ever seen in man. In every race the feet maintain their ordinary composition, in the Bosjesman as in the Patagonian. Some teratological exceptions with a tendency to heredity are nevertheless occasionally displayed, of which we shall speak in another chapter.

VII. The vertebral column is, so to speak, the fundamental portion of the skeleton, and yet it does not vary the less on that account. I shall not insist upon the differences presented by its caudal portion, merely remarking that there are races of dogs, sheep, and goats, in which the tail is so reduced as to be nothing more than a short coccyx.

The central portions themselves are known to be liable to change. Philippi tells us that the oxen of Piacentino had thirteen ribs instead of twelve, and, consequently, an extra dorsal vertebra. In the pig Eyton has observed the dorsal vertebræ vary from thirteen to fifteen, the lumbar from four

to six, the sacral from four to five, and the caudal from thirteen to twenty-three, so that the total is forty-four in the African pig and fifty-four in the English pig.

In man, the presence of one extra vertebra has occasionally been observed. These have always been isolated cases, except in one Dutch family, quoted by Vrolich. But it does not approximate to a constant character in any human group, and if such a group did exist, it is evident that the variation would here again be less than in animals, for without even reckoning the tail, it is three times stronger in the latter.

Of course, I do not take into consideration what has been so often said of men asserted to have tails. We now know better how much credit to attach to this statement. But the variations which take place in the caudal region among animals teaches us that even a considerable elongation of the coccyx in a human group, and the multiplication of the vertebræ which compose it, must not be considered à priori as a specific character.

VIII. It might have been expected that the head would have escaped modifications, on account of the importance of the organs which belong to it. But such is not the case, and here again the modifications are much greater in animals than in man. Blumenbach remarked long ago that there was more difference between the head of a domestic pig and the wild boar than between that of the White and the Negro. There are no domestic species to which the same remark cannot be applied. But I shall only remind the reader of the heads of the bull-dog, greyhound and spaniel.

The extent to which the modifications of the head can be carried is nowhere more plainly shown than in the niata cattle of Buenos Ayres and La Plata. This ox exhibits the modifications of the specific characters similar to those which the bull-dog presents among dogs. All the forms are shortened and thickened, the head in particular seeming to have experienced a general movement of concentration. The inferior maxillary bone, although itself shortened, so far exceeds the superior in length that the animal is unable to browse the

trees. The cranium is as much deformed as the face; not only are the forms of the bones modified, but also their relations, not one of which, according to Professor Owen, has been strictly preserved. This race, though perfectly established, is not therefore necessarily of less recent origin; for, as I remarked above, all the American oxen are descended from European stocks. It is already represented in the New World by two sub-races, one of which, that of Buenos Ayres, has preserved the horns, while that of Mexico has lost them.

It is scarcely necessary to remark that no human group presents anything at all analogous to this.

IX. The several facts which I have here enumerated seem to me sufficient to justify the proposition which I asserted at the commencement of the chapter, namely:-that the limits of variation are almost always more extensive between certain races of animals than between the most distant human groups.

Consequently, however great the differences existing be tween these human groups may be, or may appear to be, to consider them as specific characters is a perfectly arbitrary estimation of their value. It is, to say the least, quite as rational, quite as scientific, to consider these differences only as characters of race, and even on that account to refer all the human groups to a single species.

The legitimacy of this conclusion is incontestable. Now, I repeat, that this conclusion is sufficient to destroy the very foundation of the polygenistic theory. In reality this theory rests entirely upon morphological considerations. Its partisans, struck only by the material differences presented by the human groups, have thought it impossible to account for them, except by the admission of the existence of several species. By showing that facts of this nature can be equally well interpreted under the hypothesis of the Unity of the Species, monogenism and polygenism are, so to speak, placed on an equal footing.

CHAPTER VI.

INTERCROSSING AND FUSION OF CHARACTERS IN ANIMAL RACES; APPLICATION TO MAN.

WITHOUT even quitting the ground of morphology, it will be easy to prove which theory is most probably the correct one.

We know that naturalists consider that all individuals which pass from one to another by invisible shades belong to the same species, however different the extremes may be. All great museums contain examples of this fact.

The grounds for this conclusion are much stronger when there exists an intercrossing of characters. This intercrossing exists when a very decided and apparently exclusive character reappears in one or several individuals differing widely in other respects, and undoubtedly belonging to distinct groups. It is a case of intercrossing again, when the same character varies in such a manner as to lead, if considered apart, to the division of a natural group, and to the separation of the fractions into very different groups.

Now there is no animal species which presents these essentially morphological characters in a higher degree than man. When the human groups are studied in some detail, the difficulty does not consist in finding resemblances, but in clearly defining the differences. The more carefully they are considered, the more they disappear and become obliterated. We then understand the accounts given by most trustworthy travellers, such as d'Abbadie, of countries where the Negro and the White live side by side. In their extremes these two types are certainly very distinct. But in Abyssinia, for example, where they have long lived in contact, and intermingled, the Negro is no longer cha