This very simple consideration, which is deduced from a number of facts of detail, explains many results which cause surprise to physiologists, anthropologists, etc. After having attributed a preponderating action to the mother, Nott declares with surprise, that, in point of intelligence, the Mulatto approaches more to his white father. But is not the intellectual energy of the latter superior to that of the mother? And is it not natural that it should gain the ascendant in the struggle between the two hereditary powers? We know how far this victory can go, and how the two natures can, so to speak, divide the product of this crossing between them. Lislet Geoffroy, entirely a Negro physically, though entirely a White in character, intelligence, and aptitudes, is a striking example of it. This victory of the superior energies is again shown in another very remarkable manner, in the crossing of white and black races. The former is, of all races, most sensible to malarious influences, the latter best able to resist them. On this account it is almost exempt from yellow fever. The Mulatto inherits this double power of resistance. Nott assures us that a proportion of one fourth of black blood is as sure a protection against the yellow fever, as vaccination against the small-pox. We may now understand, that, in crossing between different races, the half-breeds possess the characters which, in each of them, predominate over the corresponding characters of the other. If the energies are in equilibrium, there will generally be a compromise. The Negro and the White differ essentially in colour and the texture of the hair; the colour of the eyes varies almost as much in one as in the other. In the Mulatto, the two first characters almost always betray the double origin of the individual; the third is uncertain. On the contrary, in half-breeds of the white and the indigenous American, the eyes and hair are almost always derived from the latter. Humboldt has remarked that these two characters are persistent even after several generations, in unilateral crossing towards the White. M. Ferdinand Denis recognised a descendant of the caciques by the eyes. On the other hand, in the same crossings, the colour of the White overcomes that of the American at the second, and sometimes even at the first generation. The crossing of the Slav and the Bouriate presents similar facts. The half-breeds invariably have the hair and eyes of the second. VIII. “In Brazil,” says Martin de Moussy, “mixed races of every origin increase, and form a new population which becomes more _indigenous_ every day, if we may use the expression, and always more similar to the white type, which, according to what takes place in the whole of South America, will, in the end, absorb all the rest.” An analogous fact has been pointed out at Buenos Ayres, in Paraguay, etc.