12 SYMBIOGENESIS 



This is another adumbration of incipient psychology as 

 involved by my bio-economic theory. The subject of mind in 

 evolution will be more fully dealt with later. 



Evidence seems, according to Prof. Keeble, to be accumu- 

 lating that frequently tropistic response is ultimately 

 connected with nutrition, and that hence, as I submit, feeding 

 habits largely determine whether an organism is to have a 

 " place in the sun " or not. Prof. Keeble here bases himself 

 on Prof. Jacques Loeb's experiments with fresh-water 

 Copepods (small Crustacea). This is what they seem to 

 indicate together with Prof. Keeble's comment. 



Copepods feed, no doubt, on algse, which can only live and grow in 

 the light. In the course of their nutrition, algae decompose carbon- 

 dioxide and liberate oxygen, so that the amount of carbon-dioxide 

 contained in the water in their immediate neighbourhood is less than 

 that contained in the darker regions of the pond. Much carbon-dioxide 

 will be correlated with limited food supply. Now it has been shown 

 definitely in the case of other animals, e.g., the caterpillars of Porthesia, 

 that they are only positively phototropic so long as they are not fed. 

 If this holds good for Copepods, their response to increased carbon- 

 dioxide becomes at once intelligible on the mnemo or associated stimulus 

 hypothesis. Thus hunger affects the tone or physiological state in such 

 a way that the Copepods respond to light by directive movements 

 whereby food supplies become available. The movement brings 

 the animals from a part of the water which contains a maximal amount 

 of carbon-dioxide to a part where, thanks to the presence and activity 

 of the green algee the food sought by the Copepods the water is not 

 fully saturated with carbon-dioxide. When the animal encounters 

 carbon-dioxide conditions, which are normally associated with hunger 

 conditions, it takes the hint and phototropes just as though it were 

 hungry. For a hungry man, a cook-shop window has an irresistible 

 attraction, whereas to the well-fed person it may offer no seduction, or 

 even be repulsive: nevertheless, "si par impossible" the odour which 

 emanates from it is very agreeable, the well-fed man may deign to sniff. 



Although the science of the physiology of form, as Prof. 

 Klebs one of its botanical pioneers states, has not progressed 

 beyond its initial stages, yet it is already strikingly 

 emphasising the importance of nutrition, and therewith, 

 as I contend, the still more fundamental importance of 



