If the defective fecundity of the Lipplappen of Java is due to the deleterious influence of climate, it is very difficult to attribute the great prolificness of the Malay-Chinese to the benignity of the same climate. Moreover, the more eastern islands, where the latter Mulattoes do not thrive, are more unhealthy than Java. There seems, therefore to result, from the facts quoted by Waitz, that the Malay-Chinese thrive where the Chinese are few in number, and that they decay where the Chinese are numerous; that is to say, that the fecundity of the hybrid population augments in proportion as the conditions favourable to a return crossing with the Malay race are present. This amounts to the same thing, namely, that the Mulattoes of the second, third, and fourth degree are more prolific than those of the first, which certainly corresponds with the laws of hybridity among animals. These facts, however, require to be verified and completed before they can serve as a basis to arrive at a definite conclusion.[43] These examples of the Mulattoes of Malasia, which we accept with reserve, tend to demonstrate that the results of intermixture do not exclusively depend on the degree of proximity of race; for there is certainly a less zoological distance between the Chinese and the Malays, and between the Malays and the Dutch, than between the African Negroes and the South Europeans. Yet the Mulattoes of the French, Portuguese, and Spanish colonies seem gifted with a much greater prolificacy than the Dutch or Chinese Mulattoes of Malasia. It is besides known that in Mexico and South America the union of the indigenous population between the Portuguese or the Spaniards has, in many localities, produced Mulattoes, the race of which seems to perpetuate itself.[44]