98 SYMBIOGENESIS 



seen, those types of organism which are most efficient in 

 symbiotic labour are also most efficient in symbiotic respira- 

 tion and in providing embryonic nutrition, some of which, at 

 any rate as " love-food," can be spared fo.r the purposes of 

 exchange with other organisms. Moreover, the most efficient 

 producers and traders among organisms are also the most 

 capable of avoiding injuries and of avoiding or escaping 

 enemies; partly because of the sympathy they enjoy, the non- 

 aggressiveness of their character, the indispensability of their 

 services, the integrity of their composition ; and partly because 

 of the superiority of their intelligence and of their social 

 organisation, their general capacity of controlling rather than 

 being controlled by the contingencies of their existence. Many 

 animal organisms, it is true, are predaceous plant-feeders, and 

 frequently the depredation of herbivores has been responsible 

 for the absence of trees and shrubs over a wide area. But 

 obviously, taken as a whole, the animal kingdom has no real 

 cause to prevent trees from securing their food by drawing on 

 the soil and so increasing their bulk. There is no real clash of 

 interests. On the contrary, in the long run, it is to the 

 animal's advantage that the tree should be allowed duly to 

 perform its labours, and that this is so, that the tree has so 

 much to offer to make its existence desirable must be and is in 

 practice an additional advantage to the tree. 



That some amount of qualification as regards the supply 

 of assimilable matter required to produce growth is necessary 

 had not totally escaped Spencer. But it has never dawned 

 upon him that there are vitally important bio-economic factors 

 involved in the production and utilisation of food. He tells 

 us, indeed, that " the value of food for purposes of growth 

 depends not on the quantity of the various organisable 

 materials it contains, but on the quantity of the material most 

 needed (quality!), that given a right proportion of materials 

 the pre-existing structure of the organism limits their availa- 

 bility, and that the higher the structure the sooner is this limit 

 reached." 



