14 SYMBIOGENESIS 



believe to be the greatest lesson for contemporary humanity to 

 derive from evolutionary studies. 



That primitive symbiosis like primitive civilisation 

 entails a certain amount of restraint, and at least some mutual 

 forbearance, may be gleaned from the fact of the occasional 

 phase of abstemiousness exhibited by Convoluta. 



Though kept for days in pure sea-water till any ordinary 

 marine animal would be ravenous, an adult C. roscoffensis 

 makes no attempt to ingest any food-substances which may be 

 added to the water. " Though tempted with diatoms, green 

 algae, starch grains, oil drops, milk, or lamp-black, it remains 

 with its capacious mouth so pursed up as to be invisible, and 

 refuses to ingest any solid food whatever. . . . Normal 

 C. roscoffensis in its natural state does not refrain from food 

 because it cannot swallow, but because it does not want to 

 eat." 



This " fasting " habit is, however, only temporary. The 

 animal can afford to exercise some restraint vis-a-vis the 

 biological environment because it has adequate biological 

 (symbiotic) providers within, and it can afford this precisely 

 in so far and so long as it duly conserves these symbiotic pro- 

 viders a number of green algal cells which it has adopted in 

 its domestic economy. 



In order to elucidate the cause of this occasional " strange 

 abstemiousness " of Convoluta, Prof. Keeble's explanation has 

 recourse to what he terms "the commonplaces of plant- 

 physiology." 



I propose to deal with his explanation at some length, being 

 convinced that vital and not yet recognised principles of 

 Bio-Economics are here concerned, and that the whole matter 

 will thus be lifted far above the level of the common-place. 

 This is what the eminent Botanist has to say: 



Green plants do not take up solid food : they manufacture it. 

 From inorganic substances, water and carbon-dioxide, which are absorbed 

 from without, the green cells of plants manufacture sugar. This 

 process, which is preliminary to nutrition, is termed by botanists 

 photosynthesis, since the energy required for the manufacture of the 



