The second point is much more serious, for if accepted without restriction, we must admit that eugenesic hybridity does not exist in mankind, and that all cross-breeds, whatever their origin, whether they are issued from nearly approaching or distant races, not merely the descendants of whites and negroes, but also of Celts and Kimris, are incapable of engendering a durable posterity. For my part, I believe that such is actually the case with certain mongrel-breeds; I believe that in the genus _Homo_, there are very unequal degrees of eugenesic hybridity; but after having recognised that eugenesic hybridity does exist between dog and wolf, hare and rabbit, goat and sheep, camel and dromedary, I am permitted to say that it also exists between certain races of men. Among the facts quoted to prove the sterility of human cross-breeds, some are of great value: and we shall examine them in the sequel; others have been wrongly interpreted, while some are far from being exact. I have already pointed out a cause of error which was not taken into account, and which occurs frequently: it is the change of climate which alone is capable of sterilising a race transplanted into the midst of another race. Before attributing a defect of fecundity to the mixed descendants of an immigrant race, we must see whether in the same country the individuals of this race are more prolific in their direct alliances. It is known, for instance, that the Mamelukes, originating from the region of the Caucasus, have never taken root in Egypt, where, nevertheless, from 1250, the epoch of their advent, until 1811, the period of their extermination, their caste has always formed a notable part of the population. They could only maintain themselves by reinforcements which they annually received from the native country, and though not half a century has elapsed since the great massacre of Cairo, there remains no trace of them on the borders of the Nile. Such being the fact, it was concluded therefrom, that the descendants of the Mamelukes and the Egyptians were hybrids of little or no fecundity. Gliddon has thus interpreted it, and Pouchet has accepted that interpretation.[21] This, however, is not the real cause of the sterility of the Mamelukes in Egypt, and Volney, who, towards the end of the last century, has carefully observed and studied this race, offers the following remarks on them: “Seeing that they have existed in Egypt for centuries, one would be apt to believe that they have reproduced themselves by the ordinary process of breeding; but if their first settlement is a curious fact, their perpetuation is not less so. For five centuries there have been Mamelukes in Egypt, yet not one of them has left a subsisting line: there exists not one family of the second generation, all their children perish in the first or second generation. _The Ottomans are nearly in the same condition_, and it is observed that they only preserve themselves from the same