238 DARWINISM AND THE PROBLEMS OF LIFE 



alone; it then passes through the whole series of 

 animals until it reaches the great monsters of the 

 deep. 



It is otherwise on the land. Here there are none of 

 the lower algse and the minute animals that we call the 

 protozoa. We have, therefore, to construct a different 

 diet-series. 



It is clear that all the higher characteristics that the 

 plants developed on land first put in their appearance as 

 root, stalk, leaves, and fibres, without being devoured 

 by the animals. The leaves were not used as food 

 until some time afterwards. It is probable that at first 

 the land-plants only served as food for the animals after 

 they had decayed, and so been modified by bacteria. 

 The earthworms, which are certainly ancient species of 

 animals, still feed in this way. Other animals may have 

 lived directly on the fungi, which were certainly nearer 

 to the diet they had been accustomed to from their early 

 days than the green plants. The fungi have a similar 

 composition and nutritive value to the animals. They 

 have no green colouring matter, but feed on organic 

 matter that the green plants have made. 



There is only a step from the eating of decayed 

 plants to the eating of carrion, and this comes close to 

 flesh-eating. We can best understand the flesh-eating 

 animals if we assume this to have been the development 

 of their diet. We are speaking, of course, only of the 

 original animals ; in the higher ones the food changes 

 according to the adaptation. Thus our former state- 

 ment, that a flesh diet comes more naturally to an 

 animal than a vegetal diet, is not inconsistent with the 



