The complexion of the Bongo in colour is not dissimilar to the red-brown soil upon which they reside; the Dinka, on the other hand, are black as their own native alluvium. The circumstance is suggestive of Darwin’s theory of “protective resemblance” among animals; and although in this instance it may be purely accidental, yet it appears to be worthy of notice. Any traveller who has followed the course of the main sources of the White Nile into the heathen negro countries, and who has hitherto made acquaintance only with Shillooks, Nueir, and Dinka, will, on coming amongst the Bongo, at once recognise the commencement of a new series of races extending far onwards to the south. As trees and plants are the children of the soil from which they spring, so here does the human species appear to adapt itself in external aspect to the red ferruginous rock which prevails around. The jet-black Shillooks, Nueir, and Dinka, natives of the dark alluvial flats, stand out in marked distinction to the dwellers upon the iron-red rocks, who (notwithstanding their diversity in dialect, in habit, or in mode of life) present the characteristics of a connected whole. Of this series the tribes which must be accounted the most important are the Bongo, the Mittoo, the Niam-niam, and the Kredy, all of which are equally remarkable for their entire indifference to cattle-breeding. The whole of these, especially the women, are distinguished for the reddish hue of their skin, which in many cases is almost copper-coloured. It cannot be denied that this red-brown complexion is never entirely wanting, even amongst the darkest skins that are found in the lowlands; but the difference between their complexion and what is ordinarily observed among the Bongo is only to be illustrated by the contrast in colour between a camellia leaf in its natural condition and after its epidermis has been removed.