We see that the variation between races is in the horse twice as great as in man, nearly three times in the sheep and rabbit, and four times as much in the dog. The difference is perhaps even more striking in the goat and ox, judging from the terms of comparison used by several travellers. If, after having studied the various dimensions of the body, we compare the differences in proportion presented on the 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.