ASSIMILATIVE COLOURATION. 397 
and a dull dark crimson.”* As further remarked :— ‘‘ In the 
dark bosom of the earth a green leaf would be quite useless, and ~ 
as a matter of fact there is not a single plant whose green tissue 
is situated in the depths of the soil.” + 
Even the obscure problem of the colouration of mankind may 
have originally—and before migration became such an important 
factor in modification—been due to a more or less assimilative 
colouration. Thus, in Central Africa, Schweinfurth has re- 
marked :—“ The complexion of the Bongo in colour is not 
dissimilar to the red-brown soil on which they reside; the Dinka, 
on the other hand, are black as their own native alluvium.” And 
again :—‘‘ 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, notwith- 
standing their diversity in dialect, in habit, or in mode of life, 
present the characteristics of a connected whole.” {| Dr. Schwein- 
furth also observes that ‘‘the circumstance is suggestive of 
Darwin’s theory of ‘protective resemblance’ among animals.” 
But as such a view of protective resemblance has not hitherto 
been applied to the colour of mankind, and as it would be ex- 
tremely difficult to defend such a proposition, it might at least be 
suggested as probable that we have here another survival of an 
original and somewhat universal assimilative colouration. Similar 
observations have been made by many travellers. Livingstone 
describes the colour of the soil composing the plain of the 
Kalahari Desert as in general “light-coloured soft sand, nearly 
pure silica,” § and that the Bushmen inhabiting these plains are 
* Kerner and Oliver, ‘ Nat. Hist. Plants,’ vol. 1. pp. 889-90. 
+ Ibid. p. 665. . 
{ ‘The Heart of Africa,’ vol. i. p. 261. 
§ ‘ Miss. Travels and Researches in 8. Africa,’ p. 47. 
