236 DARWINISM AND THE PROBLEMS OF LIFE 



inorganic. They thus exercise their power, not solely 

 for themselves, but also for the whole animal kingdom. 

 The animals can only cover their loss of organic sub- 

 stance from disintegration by obtaining albuminoids 

 ready made, which they merely convert into living 

 matter. They either take their food from the plants, 

 or they satisfy their need of organic food by devouring 

 their fellows, and these must have built up their frames 

 on vegetal matter. The groundwork of all life is found 

 in the plants ; without them the animal world is 

 unthinkable. 



Let us now consider a world in miniature, a pond, in 

 order to see the successive steps in the provision of 

 food. There must first of all be plants, if any living 

 substance is to be formed at all. In the pond these are 

 chiefly algae, tiny green vesicles, which often swim freely 

 about. These algae form the food of the water-fleas, 

 the crustaceans of which we spoke at the beginning of 

 this chapter. Most of the other animals live on these 

 fleas, as also do the fishes, which feed almost exclusively 

 on water-fleas in their earlier stages. The fleas are, 

 therefore, an important connecting link in the economy 

 of Nature. 



Even from this instance we see that it is not the 

 higher plants that form the groundwork of the nutritive 

 scale. This will easily be understood from the fact that 

 the higher plants are very complex structures, with their 

 stem and roots, leaves and flowers ; they must have 

 been developed at a late date, when there were already 

 plenty of animals. Thus the first " angiosperms " or 

 all our foliage-trees and shrubs, and many of our herbs 



