TROPICAL NATURE 



running to its burrow, is made conspicuous to the sportsman, 

 and no doubt to all beasts of prey, by its upturned white tail. 

 But this very conspicuousness while running away, may be 

 useful as a signal and guide to the young, who are thus 

 enabled to escape danger by following the older rabbits, 

 directly and without hesitation, to the safety of the burrow ; 

 and this may be the more important from the semi-nocturnal 

 habits of the animal. If this explanation is correct, and it 

 certainly seems probable, it may serve as a warning of how 

 impossible it is, without exact knowledge of the habits of an 

 animal and a full consideration of all the circumstances, to 

 decide that any particular coloration cannot be protective or 

 in any way useful. Mr. Darwin himself is not free from such 

 assumptions. Thus, he says : " The zebra is conspicuously 

 striped, and stripes cannot afford any protection on the open 

 plains of South Africa." But the zebra is a very swift 

 animal, and, when in herds, by no means void of means of 

 defence. The stripes therefore may be of use by enabling 

 stragglers to distinguish their fellows at a distance, and they 

 may be even protective when the animal is at rest among 

 herbage the only time when it would need protective colour- 

 ing. Until the habits of the zebra have been observed with 

 special reference to these points, it is surely somewhat hasty 

 to declare that the stripes "cannot afford any protection." 1 



Colowr proportionate to Integumentary Development 

 The wonderful display and endless variety of colour in 

 which butterflies and birds so far exceed all other animals, 

 seems primarily due to the excessive development and endless 

 variations of the integumentary structures of these two 

 groups. No insects have such widely expanded wings in pro- 

 portion to their bodies as butterflies and moths ; in none do 

 the wings vary so much in size and form, and in none are they 

 clothed with such a beautiful and highly-organised coating of 

 scales. According to the general principles of the production 

 of colour already explained, these long continued expansions of 

 membranes and developments of surface-structures must have 

 led to numerous colour-changes, which have been sometimes 

 checked, sometimes fixed and utilised, sometimes intensified, 

 1 For further information on this point, see Darwinism, p. 220, 



