v] LATER PROGRESS 125 



that eat green plants ; many bacteria feed on the 

 dead tissues of animals and plants, bringing about as 

 a result of their activity the phenomenon known as 

 decay ; and fungi live to a great extent on the 

 substances produced during decay. Meanwhile, how- 

 ever, the waste products of the current of metabolism 

 and the final products of decay, which come eventu- 

 ally to be degraded to simple stable substances such 

 as water, carbon dioxide, ammonia, and nitrates, get 

 diffused in the soil, and form the basis once more of 

 the green plant's activity. 



In a sense, therefore, the whole organic world 

 constitutes a single great individual, vague and badly 

 co-ordinated it is true, but none the less a continuing 

 whole with inter-dependent parts : if some accident 

 were to remove all the green plants, or all the bacteria, 

 the rest of life would be unable to exist. This in- 

 dividuality, however, is an extremely imperfect one- 

 the internal harmony and the subordination of the 

 parts to the whole is almost infinitely less than in the 

 body of a metazoan, and is thus very wasteful ; instead 

 of one part distributing its surplus among the other 

 parts and living peaceably itself on what is left, the 

 transference of food from one unit to another is 

 usually attended with the total or partial destruction 

 of one of the units. 



Within this biggest system, nature has been per- 

 sistent in her efforts to create other "naturally-isolated 



