If everything shows us that zoosperms, proceeding from very different animals, can equally fecundate any given ovum,--if we even admit that we have no good reason for rejecting the theory that each ovum can be impregnated by different kinds of zoosperms, it is very easy, on the contrary, to account for the fact that offspring will have no chance of life, except so far as the two parents show a sufficient identity, but which we cannot regard as fit to characterise species. As the produce of two organisms, a descendant ought always to be considered as the result of two united halves fitted together, and combined one with the other. If the two halves are identical, the animal is like its progenitors in everything. If the two beings, who have endeavoured to unite themselves, are too dissimilar, the two forces cannot combine, and there is either no produce, or it is arrested in its development from the first moment of its embryo life. If the two forces, or the sum of the two forces, have a certain amount of common direction, they can produce a new being, but an imperfect one, and which will not have all the conditions of existence like its parents; it will not have genital power, and consequently will not be fitted to become the founder of a series of individuals similar to itself, succeeding it through time, “naturally, regularly, and indefinitely.”[246] Putting on one side the power of reproduction, we must attend solely to the union of different human races with regard to vitality of produce, and let us see what observation will teach us on this subject. Jacquinot states, that “one can scarcely quote any cross between Australians and Europeans.” When the ancient inhabitants of Van Diemen’s Land, reduced to the number of two hundred and ten, were taken from Flinder’s Island, not only had the union of the women with the unscrupulous convicts been unable to form a distinct race, but only two adults were found who were the produce of these unions.[247] “The Mulattoes,” says Nott, “are the shortest-lived of any of the branch races; when they unite amongst themselves, they are less prolific than if united to one or other of the branches.[248]” This assertion is especially true concerning the cross-breeds born of Negroes and inhabitants of the north of Europe. At Java, crosses between Malays and Dutch appear not to be able to reproduce beyond the third generation.[249] “The _half-caste_ of India,” says Warren, “comes to a premature end, generally without reproduction; and if there are any offspring, they are always wretched and miserable.”[250]