ASSIMILATIVE COLOURATION. 471 
belonging to all classes, I cannot avoid the conclusion that the 
curiously-arranged colours of many Antelopes, though common 
to both sexes, are the result of sexual selection primarily applied 
to the male.” * And he subsequently remarks: ‘ Nevertheless, 
he who attributes the white and dark vertical stripes on the flanks 
of various Antelopes to this process will probably extend the 
same view to the royal Tiger and beautiful Zebra.” + Mr. Wallace 
estimates the derivative process of spots and stripes as a purely 
protective one:—‘‘ In mammalia we notice the frequency of 
rounded spots on forest or tree-haunting animals of large size, as 
the forest Deer and the forest Cats; while those that frequent 
reedy or grassy places are striped vertically, as the Marsh Ante- 
lopes and the Tiger.” And again: ‘‘It is the black shadows of 
the vegetation that assimilate with the black stripes of the Tiger; 
and in like manner, the spotted shadows of leaves in the forest 
so harmonize with the spots of Ocelots, Jaguars, Tiger-cats, and 
Spotted Deer, as to afford them a very perfect concealment.” f 
This last view seems borne out by all the facts at our disposal, 
and as adaptation implies a previous state of variation, which 
again predicates a more or less stable condition from which 
variation arose, we come to the conclusion that the pre-variable 
condition was a unicolorous one, and from the data—scanty 
indeed—at our disposal, are inclined to suggest that the uni- 
colorous hue was originally due to assimilative colouration. The 
wild Horse of Asia is said to be of a dun colour, while those 
of South America are described as commonly chestnut or bay 
coloured.§ Why is this ?—the question bristles with present 
difficulties. In the writings of pre- and anti-Darwinian naturalists 
are often found remarks and statements unconsciously supportive 
of the future theory. Thus Charles Waterton, in describing the 
faunistic features of the Demerara forest, writes: ‘‘ The naturalist 
may exclaim that nature has not known where to stop in forming 
new species, and painting her requisite shades ’”’||; while Frank 
Buckland from a teleological point of view had pointed out that 
the striped coat of the Tiger was ‘‘ most suited” to his environ- 
* Descent of Man,’ 2nd edit. p. 544. + Ibid. p. 546. 
} ‘Darwinism,’ pp. 199, 200. 
§ Huxley, ‘Collected Essays,’ vol. ii. p. 426. 
|| ‘ Wanderings,’ Wood’s edit. p. 94. 
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