258 SYMBIOGENESIS 



therefore a vital difference between plant and animal, and their 

 mutual relations involving work had to be shaped, as we have 

 seen, in accordance with symbiotic reciprocities. Neither can 

 grow by merely ingesting "like elements with itself." In 

 order to grow they must first earn their living by work. 



So far from depending on " like elements with them- 

 selves," it may be said that they really depend on that which 

 is unlike themselves, though bio-economically and physio- 

 logically adequate, i.e., on cross-feeding. That plant and 

 animal in following their normal nutritive instincts can be 

 seen actively to transmute or integrate material coming from 

 lower kingdoms into nobler biological currency (nutritional 

 " amphimixis ") is indeed the most important fact to be noted 

 in connection with growth. Their similarity consists prin- 

 cipally in the fact of a mutual bio-economic purpose under- 

 lying their respective specialisation, although the plant here 

 shows itself superior in creative power. Otherwise plant and 

 animal require unlike material for unlike (though reciprocal) 

 purposes. In his chapter on " Development," Spencer indeed 

 contradicts his assertion that an organism requires for its food 

 elements like itself. " And when we pass to the superior 

 classes of organisms land-plants and land-animals we find 

 that, chemically considered, they have little in common either 

 with the earth on which they stand or the air which surrounds 

 them." "Thus, on contemplating the various grades of 

 organisms in their ascending order, we find them more and 

 more distinguished from their inanimate media , in structure, 

 in form, in chemical composition, in specific gravity, in 

 temperature, in self -mobility." (Italics mine.) 



He almost may be said there to go so far as to put the case 

 of genuine adaptation v. "extreme determination," i.e., of 

 physiology v. pathology. " We may say that in proportion 

 as an organism is physically like its environment, does it 

 remain a passive partaker of the changes, as it is endowed with 

 power of counteracting such changes, it exhibits greater unlike- 

 ness to its environment." 



