io6 LIFE : OUTLINES OF GENERAL BIOLOGY 



the circles of many other hves. Gilbert WTiite's letter on the influence 

 of earthworms in Nature, written in 1777, was the precursor of 

 Darwin's Formation of Vegetable Mould, published more than a 

 hundred years afterwards (1881) ; and central to both is the idea of 

 the correlation of organisms — the vital linkages that bind living 

 creatures together in mutual dependence and interaction. This is 

 the idea of the Web of Life. 



The frequency of these inter-relations is partly due {a) to the 

 necessary Hnkagcs between the Animal Kingdom and the Plant 

 Kingdom, for all animals are in the long run dependent on plants; 

 and {b) to the fact that the scheme of Animate Nature implies a 

 sequence of re-incarnations or re-embodiments, one organism 

 depending on another for sustenance. Here also account must be 

 taken of the r61e of Bacteria in the circulation of matter. 



But some other factor is needed to account for the frequency 



ANT eater! \ ( ^ PARTNER 



'INFUSORIANS 



CUE5T5 \l ( / \DESTROYINO 



IWOOD 



CIRCULATION 

 OF SOIL 



Fig. 29. 



Diagram of Inter-relations, suggesting how the circle of one life, e.g. Ter- 

 mites, intersects many other circles, e.g. guest-insects, ant-eater enemy, 

 partner infusorians, the trees destroyed, and the soil. 



of vital linkages in Animate Nature, and that factor is to be found 

 in the spurs implied in the struggle for existence, and from this we 

 can hardly separate the dynamic quality of the \ngorous organism. 

 The struggle for existence is due to the rapid multiphcation shown 

 by most living creatures, to the changefulness of the physical 

 environment, and to the scheme of nutritional changes that evolution 

 has wrought out; and it cannot be separated from the quality of 

 insurgence and unsatisfiedness that marks most organisms that do 

 not simply follow the line of least resistance. The spur of struggle 

 and the urge for "more" are so incessant that living creatures are 

 rarely slow to use opportunities, whether consciously realised or 

 but rcflrxly reacted to. Thus has arisen the great variety of inter- 

 relations, in which some advantage is gained on one side or on both 

 sides by means of some sort of vital hnkage. 



INTER-RELATIONS CLASSIFIED. -An attempt must be made 

 to classify the numerous inter-relations which are so charac- 



