92 THE MEANING OF EVOLUTION 



their place in the struggle for life outside and hunt 

 their own living, one or more of them has succumbed. 



After the battle for food comes the struggle for 

 shelter. For most animals there is no such thing as 

 shelter. They are exposed to the inclemencies of the 

 weather and to the depredations of their enemies with- 

 out the means of retiring into any situation which 

 might protect them. In the higher animals, especially 

 when they are warmer blooded and their bodies must 

 be kept at a higher temperature, some form of cover- 

 ing has come to be almost universal. 



Though comparatively few animals are prepared to 

 seek shelter from the cold, all of them have enemies 

 against whom they must battle. These foes may wish 

 to eat them or may simply wish to get them out of 

 the way. In either event this struggle is so persist- 

 ent and so keen that after starvation it is probably the 

 source of the largest loss to the animal kingdom. 



Considering first the feeding habits of animals, we 

 find they are exceedingly varied. Some creatures sim- 

 ply engulf other and more minute animals, often only 

 microscopic in size, in such quantities as to satisfy 

 their hunger. Others, feeding upon larger plants or 

 animals, must have some means of breaking off par- 

 ticles of this food; still others confine themselves en- 

 tirely to nutritious fluids, and must have organs 

 adapted to this particular type of food. 



