SYMBIOSIS 63 



of starvation, but is at all events hastened by poisoning due to the 

 accumulation in the tissues of the products of nitrogenous metabolism. 

 According to this view, uninfected C. roscoffensis dies as the consequence 

 of an aggravated attack of " uric acid trouble." 



And thus Prof. Keeble is almost driven by the logic of his 

 results to conclude that at bottom we are here dealing with a 

 parasitic diathesis, which, as it is the fundamental cause of 

 retrogression in both partners, may be somewhat relieved by 

 virtue of that rudimentary symbiosis still inherent in the 

 arrangement ; but becomes acute and aggravated if this 

 modicum of symbiosis is not reached. 



True, Prof. Keeble guards himself immediately by 

 qualifying his suggestion as " somewhat fantastic " ; but as he 

 brings forward further evidence in support of that suggestion, 

 we can see that it is only the novelty of the diathesis-view 

 which causes this perplexity. 



Although the evidence provided in favour of this hypo- 

 thesis may be somewhat slender in the case of C. roscoffensis, 

 it is decidedly more plentiful in the case of C. paradoxa. " A 

 far more greedy feeder than the green species, its accumula- 

 tions of nitrogenous waste substances are much larger than 

 those of its ally." 



Prof. Keeble apparently does not realise that the luxuriant 

 growth of cells which here results from such a soil, in reality 

 amounts to an inflation which is sure to be followed by 

 exhaustion and by precarious biological concomitants. He 

 wavers between a "symbiotic" or a "parasitic" explanation, 

 with an inclination towards the latter, as is apparent from the 

 following : 



In such Capuan circumstances, the algal cells grow and divide 

 luxuriantly. Their photosynthetic activities increase, for only in the 

 presence of plentiful supplies of nitrogen does the chlorophyll-apparatus 

 work well. Large quantities of carbohydrate material are produced in 

 the algal cells enough for the needs of these cells and for those of the 

 animal. All goes well, so well indeed that C. roscoffensis, less 

 conservative than its ally, contents itself entirely with the supplies of 

 food-material, of fat, and also of organic nitrogen compounds, provided 

 by its green cells and abandons the practice of fending for itself. 



