an unlimited fecundity, both in their direct alliances and with either of the parent races, whence we have inferred that eugenesic hybridity really exists in mankind.

We intend now to investigate the results of certain intermixtures more disparate, and review a number of facts tending to the conclusion that all human cross-breeds are not eugenesic.

Let us observe at the outset, how far the phenomena of eugenesic or non-eugenesic hybridity may affect the solution of the great question pending between the Monogenists and the Polygenists.

What in animals in general, characterises the eugenesic hybridity, is the unlimited fecundity of mongrels of the first degree between themselves. It is by no means necessary that the parent species should be as prolific in their crossings as in their direct unions, nor that the mongrels should be as productive as their parents, as large, as strong, and as long-lived, etc. Supposing, for instance, that the she-wolf conceives with more difficulty with the mastiff than with her proper mate; supposing even that this crossing is only efficacious by way of exception; that it succeeds only once out of ten, instead of succeeding constantly as it occurs in animals of the same species; it would be sufficient, if in this tenth case the mongrels are very prolific to pronounce the crossing eugenesic. Supposing also, that the hybrid wolf-dogs of the first degree produced only litters of about two or three, that is to say, only half the number usually produced by she-wolves and bitches, the result would be that this intermediate race would breed less rapidly by half than the pure species; but, provided the productiveness of the mongrels does not descend below the degree necessary for the preservation of the species, and provided it can repair the loss at every generation, the crossing would still be eugenesic, nor would it cease being so, even if the breed were only half as strong as their parents, and only half as long-lived.

Remarks on the interpretation of human hybridity

When, therefore, a physiologist wishes to demonstrate the existence of that degree of hybridity which we have termed eugenesic, he selects two perfectly recognised distinct species of animals, crosses them, studies their breeds, and if he finds that they are indefinitely prolific, it is sufficient for him to affirm the existence of eugenesic hybridity—that is to say, that the physiological definition of the species is unacceptable. But when a zoologist, in studying two races of animals, the specific determination of which is still contested, endeavours to establish that these two races are merely varieties of the same species, and when in order to weaken the differential anatomical characters pointed out by his adversaries, he invokes the physiological analogy exhibited by intermixture, we have a right to expect more than a partial demonstration. We must first prove that the intermixture of the two races constitutes a case of eugenesic hybridity; for if the cross-breed are not between themselves indefinitely prolific, it is certain that the two races are not of the same species. This first point being established, would not yet lead to any conclusion, since animals of different species may engender eugenesic breeds. He must, therefore, completely analyse all the phenomena of reproduction and prove that they are exactly the same in the parent races and in the hybrid race. It is not merely the sexual analogy but the sexual identity which must be rendered evident; for from his point of view, it is not sufficient that the two races in question should be homogenesic in some degree, they must be entirely homogeneous, and the least genital difference becomes an argument against the proposition he sustains. If the cross-breed, though very prolific, are less so than their parents, or less productive in their crossings than their direct alliances; or, finally, if the investigation of these crossings exhibits any functional inequality, it might become very probable that the two races do not belong to the same species. Such would also be the case if the cross-breed were less strong and vivacious than the individuals of the pure race, or if one of the crossings is more productive than the inverse crossing, as is observed in certain cases of hybridity, which approach more or less of unilateral hybridity. The existence of one of these phenomena might prove that the two races are not homogeneous, and might lead us to think that they are not of the same species.

The monogenists, who have based the demonstration of the unity of the human species upon the physiological character of the prolificacy of the cross-breeds, have not taken into account these elements. They have confined themselves to the assertions that all human races can produce cross-breeds, and that all these breeds are prolific. Now, admitting for a moment that these assertions are exact, the conclusion they have drawn from them is still contestable, until they can demonstrate that the study of these cross-breeds reveals no genital inequality between the parent races.

But what becomes of their argumentation, if it be proved that all intermixtures are not eugenistic, that is to say, that certain mongrels are not between themselves indefinitely prolific; that other cross-breeds become sterile in the first generation; and, finally, that certain races are so little homogenesic, that the birth of cross-breeds of the first degree is more or less exceptional? If one of these propositions can be effectually established, the monogenists would have little cause to congratulate themselves for having appealed to physiology. They would, on the contrary, have furnished their adversaries with deadly weapons, and their doctrine would be demolished on the battle field they have themselves chosen.

The facts I intend to exhibit tend to prove that it was a great error to consider all intermixtures of men as eugenesic. Obliged as I am to refer to testimonies which, perhaps, do not always exhibit a desirable precision, some doubts may hover over my conclusion; this much, however, will result from this sketch, that the examination of the laws of hybridity is far from being favourable to the doctrine of monogenists.

We shall study the cross-breeds both in relation to their fecundity and their physical and moral validity; for, from our point of view, it is sufficient to prove that certain cross-breeds are inferior to the parent races, as regards longevity, vigour, health, and intelligence, to render it very probable that the two races are not of the same species.