460. THE ZOOLOGIST. 
beauty.” * This cannot be taken as an instance of pure but only 
partial assimilative colouration, but is sufficient to prove that 
colour may be largely derived from the mineral constituents of 
the earth’s surface, and in this way can scarcely be altogether 
ascribed to the action of ‘“‘ natural selection.” These bright wing 
feathers may have subsequently served the purpose of ‘‘ recogni- 
tion markings” ?, but seem certainly not derived directly for that 
purpose. 
A better example may be found in the Red Hartebeest 
(Alcelaphus cokei). Sir H. H. Johnston narrates of this species : 
‘Being a deep red-brown in colour, and standing one by one 
stock-still at the approach of the caravan, it was really most 
difficult and puzzling sometimes to know which was Hartebeest 
and which was ant-hill; for the long grass hiding the Antelope’s 
legs left merely a red-humped mass, which, until it moved, might 
well be the mound of red earth constructed by the white termites. 
The unconscious mimicry was rendered the more ludicrously 
exact sometimes by the sharply-pointed flag-like leaves of a 
kind of squill—a liliaceous plant—which frequently crowned the 
summit of the ant-hill or grew at its base, thus suggesting the 
horns of an Antelope, rather with the head erect, or browsing 
low down. The assimilation cannot have been fancied on my 
part, for it deceived even the sharp eyes of my men; and again 
and again a Hartebeest would start into motion at twenty yards 
distance, and gallop off, while I was patiently stalking an ant-hill, 
and crawling on my stomach through thorns and aloes, only to 
find the supposed Antelope an irregular mass of red clay.” t 
This would seem to be almost an instance of acquired or active 
mimicry on the part of this animal. Here the whole question to 
be considered is what was the original home of this Red Harte- 
beest? Is it a creature of these red-earthed plains, the character 
of which is so prominently shown in these gigantic ant-hills ? 
* ¢Cassell’s Nat. Hist.,’ vol. iii. p. 380. Dr. Sharpe has subsequently 
expressed further doubt on the suggested cause of this colouration: ‘The 
Touracous are birds which live in trees, and do not apparently descend to 
the ground, while the red feathers have been assumed by specimens in 
captivity, some of which moulted more than once” (‘ Roy. Nat. Hist.,’ 
vol. iv. p. 18). 
+ ‘The Kilima-Njaro Expedition,’ p. 65, 
