SYMBIOSIS 59 



What are the various full and normal " customs " obtain- 

 ing between those physiological complements? 



Did we not find, for instance, that the very material for 

 the eggs of Convoluta is provided by the green cells? Have we 

 not now learned that the whole "business " of the animal is 

 inseparably bound up with that of the plant, and vice versa? 



What the animal wants is good currency direct from the 

 physiological mint, i.e., the plant, and won by appropriate 

 biological symbiosis, and as regards customs it is desirable to 

 adopt the Pythagorean maxim : "Fix upon that course of life 

 which is best and habit will make it the most delightful." 

 Convoluta has not fixed upon the best course of life but has 

 retrogressed from it. The divorce from biological symbiosis, 

 however, is not yet complete, and some former " custom " still 

 survives. "Custom" per se, of course, is inadequate as an 

 explanation; for "custom" may have deteriorated. Bad 

 customs must prevent rather than promote ordered develop-- 

 ment. The effect of beneficial ancient Convoluted " custom " is 

 shown in the phase of comparative "abstemiousness," the 

 effect of evil recent custom in the phase of voraciousness, parti- 

 cularly by C. paradoxa. Customs are no more fixed than 

 species, and, indeed, the change of species is primarily, I 

 assert, due to a change of " customs" the most prominent in 

 importance being the feeding "customs." Hormones, like 

 enzymes, vitamines and alkaloid poisons, only follow in the 

 wake of bio-economic "customs." They determine develop- 

 ments precisely in so far as the efficacy deputed to them has in 

 the past been evolved by (good or bad) bio-economic 

 " customs." 



The latter-day "intimacy" of Convoluta and alga? has 

 its antecedents in primordial relations of a different order. 

 " The association between green cells and animals does not 

 begin with the entrance of the green cell or its colourless 

 antecedent into the body." The acquaintance began with an 

 identity of phototropistic response. Since we have already seen 

 that frequently tropistic response is ultimately connected with 



