218 
DARWINISM 
CHAP. 
The wonderful diversity of colour and of marking that pre¬ 
vails, especially in birds and insects, may be due to the fact 
that one of the first needs of a new species would be, to keep 
separate from its nearest allies, and this could be most readily 
done by some easily seen external mark of difference. A few 
illustrations will serve to show how this principle acts in nature. 
My attention was first called to the subject by a remark 
of Mr. Darwin’s that, though, “ the hare on her form is a 
familiar instance of concealment through colour, yet the 
principle partly fails in a closely allied species, the rabbit; for 
when running to its burrow it is made conspicuous to the 
sportsman, and no doubt to all beasts of prey, by its upturned 
Avhite tail.” 1 But a little consideration of the habits of the 
animal will show that the white upturned tail is of the greatest 
value, and is really, as it has been termed by a writer in The 
Field , a “signal flag of danger.” For the rabbit is usually a 
crepuscular animal, feeding soon after sunset or on moonlight 
nights. When disturbed or alarmed it makes for its burrow, 
and the white upturned tails of those in front serve as guides 
and signals to those more remote from home, to the young and 
the feeble ; and thus each following the one or two before it, all 
are able with the least possible delay to regain a place of 
comparative safety. The apparent danger, therefore, becomes 
a most important means of security. 
The same general principle enables us to understand the 
singular, and often conspicuous, markings on so many gregarious 
herbivora which are yet, on the whole, protectively coloured. 
Thus, the American prong-buck has a white patch behind 
and a black muzzle. The Tartarian antelope, the Ovis poli 
of High Asia, the Java wild ox, several species of deer, and a 
large number of antelopes have a similar conspicuous white 
patch behind, which, in contrast to the dusky body, must enable 
them to be seen and followed from a distance by their fellows. 
Where there are many species of nearly the same general size 
and form inhabiting the same region — as with the antelopes 
was the same. This is precisely what we should expect if the symmetry is not 
the result of a general law of the organisation, but has been, in part at least, pro¬ 
duced and preserved for the useful purpose of recognition by the animal’s 
fellows of the same species, and especially by the sexes and the young. See 
Proc. of the Am. Ass. for Advancement of Science, vol. xxx. p. 246, 
1 Descent of Man, p. 542. 
