94 DARWINISM AND THE PROBLEMS OF LIFE 



military dress of the particular period ; and this was 

 certainly not meant to be merely defensive, but also to 

 make the wearer seem formidable as, for instance, 

 skins with animal helmets, waving plumes, etc., or at all 

 events to give him a greater appearance of strength and 

 life and boldness, in which bright colours would be 

 useful. But it is impossible for all the details of the 

 composition and design of animal colours to have arisen 

 in this way. It is also inadequate to explain the 

 undoubted fact that they act as distinguishing characters 

 of a species. As such they play a great part in the life 

 of animals ; it is easy to see that those animals will 

 propagate best which can recognise their kind most 

 quickly. Perhaps many light colours arose in this way, 

 and they could be preserved and accentuated in the 

 male, but not in the female, which absolutely needs a 

 neutral tint in order to sit unobserved in the neutral- 

 tinted nest or on the ground. Only in this way could 

 the mother and her eggs, and later the helpless young 

 ones, escape the fatal eye of their enemies. The eggs 

 of birds that hatch on open nests are also protected by 

 fitting colours that save them from many eyes ; while 

 birds that sit in hollows generally have white eggs. 

 There is an exception in a number of blue eggs that are 

 found in open nests. An attempt has been made 

 recently to explain their colour on the theory that the 

 blue is particularly favourable to metabolism. 



There are many features that are common to both 

 sexes. These are usually confined to particular spots, 

 and can do no injury to the animal when it sits quietly. 

 In this group we have a whole series of colours that 



