218 DARWINISM 



The wonderful div. ity 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 

 white 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. 



