A NATURALIST IN BRAZIL 



expanded into lateral lobes, and therefore can never be seen. Even 

 entrails often display the loveliest colours. But in the case of most 

 colours we do realize that they have been chosen because they are 

 essential to the life of the wearer. The two English scientists, Darwin 

 and Wallace, were the first to recognize the great significance of 

 colour in the animal world. 



There are two points of view from which we can perceive and 

 understand their significance. In the first place, the coloration of a 

 living creature is protective. Anyone who keeps his eyes open will 

 often have occasion to realize how difficult it is to detect even 

 large animals in a state of nature, because their colouring blends 

 with their environment. Think of green insects in the grass, or brown 

 insects on the trunk of a tree ! Protective colouring makes it possible 

 for the animal to make itself invisible to its enemies, but it also 

 enables the beast of prey to approach its victim unnoticed. 



But while the animals must be able to conceal themselves from 

 their enemies, they must at the same time be recognized by their 

 fellows. The male must be able to find the female, and the female 

 must know that this time she is not being pursued by an enemy; 

 otherwise the species would not multiply. Consequently the animals 

 have need of tokens by which they can recognize their own species. 

 And it is these signs that make them stand out from their environ- 

 ment, and reveal this presence to their fellows. 



Protective coloration and the tokens by which a species is recog- 

 nized call for absolutely diflferent kinds of behaviour, and it is most 

 interesting to observe how Nature has contrived to accomplish 

 her twofold task. Since the animals possess several senses, the dis- 

 covery of the mate may, if the biological conditions of the animal 

 permit, be entrusted to some other organ than the eye. 



In the mammals the nose is the guiding organ, and so in this 

 class each species has had to evolve a special odour, which becomes 

 intensified during oestrum. This odour leads the seeker all the more 

 surely inasmuch as the mammal moves about on the ground and 

 leaves a scent behind it. Animals of the same species are able to 

 follow such a trail for a considerable distance, and so we may see 

 that not only do the fox and the marten run with their noses to the 

 ground during all their excursions, but that the roebuck too follows 

 his doe with lowered head. 



But since the mammals recognize those of their own species by 

 the sense of smell, the outside of the body may be given a protective 

 coloration. And as a matter of fact, the majority of the mammals 



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