SYMBIOSIS AND THE BIOLOGY OF FOOD 267 



My thesis as regards feeding is this : " Nature abhors 

 perpetual in-feeding." By the term "in-feeding" I mean 

 the indolent appropriation of food manufactured by close 

 relatives, and the correlated shirking of the economic duty of 

 production, or of mutual service in some kind. By " cross- 

 feeding," on the other hand, I mean feeding on material — • 

 generally of another " kingdom " — ^which does not involve 

 the non-symbiotic devouring of organism by organism — the 

 killing of the goose which lays the golden eggs. Once more 

 we may infer that one implication of the underlying truth is 

 that the " self -regarding " activities are to be restrained 

 and regulated in accordance with the contingencies of existence. 

 These contingencies are mainly bio-economic and sociological, 

 i.e. they have regard to wide biological usefulness — ^for instance, 

 to the welfare of biological partners, to accommodate whom 

 must be, and is, a prime concern of biological relation. 



The long-standing relation between bee and flower also 

 rests upon the " cross-feeding " principle, which alone allows 

 of perfect ' ' live and let live. ' ' If the bees transgress even against 

 " live and let live," by felonious ways of obtaining the nectar, 

 they become " debauched." Just as the parasitic mode of 

 life is generally derived from a previous predatory one, so, I 

 contend, the latter is derived from a previous cross-feeding 

 and symbiotic one. Cross-feeding, in other words, is primitive, 

 representing the norm and integrity of life. 



Darwin stated that pollination by insect agency might be a 

 great gain to a plant, though nine-tenths of the pollen be eaten 

 by the insect, so long as at least a cross was effected. The full 

 implication of this observation is that the establishment of 

 sound and progressive symbiotic relations in the world of life 

 reacts favourably on the plant. The plant is thus able to 

 command reliable and systematic counter-services, obviating 

 the far greater waste of pollen in wind-fertilisation. Ability 

 to rely upon biological S3mibiosis in this case means great 

 constancy of " crossing " and, hence, a more frequent gain of 

 vigour and health. And it means more : the biological nexus, 

 once satisfactorily established, acts as a stimulant to the plant 

 to perfect its own domestic Symbiosis, conforming more and 

 more to the contingencies of biological Symbiosis, i.e. of wide 

 and general usefulness (co-adaptation). It is as though the 

 plant, thus reliably allied, felt a higher call in life than one 

 entertaining only casual biological relations. 



It is an indisputable fact, emphasised by Darwin, that 

 entomophilous plants (relying on wind-fertilisation) are higher 

 in the scale than anemophilous (relying on animal agency). 

 They have a higher output of valuable substances — for the 

 reasons already given, namely, that they have earned and enjoy 



