THE aREEN CELLS OF COxWOLUTA ROSCOFPENSIS. 199 



(6) The green partial cells wliicli result are incapable of 

 independent existence. 



Section VI. The Significance and the Consequences op 

 THE Association op Animal and Green Cell. 



The relation between Convoluta and its green cells has 

 sometimes been regarded as an example of parasitism, the 

 parasite being the green cell and the Host the animal. That 

 this is an erroneous view we have already demonstrated. 



More usually it is assumed that both partners in the 

 association receive advantage therefrom, and consequently 

 the relation is considered to be symbiotic. 



It is obviously important, if such a term as " symbiosis " is 

 to retain any value whatever, that a detailed examination of 

 each case which appears to fall into this category should be 

 made before it is relegated thereto. This is the purpose of 

 the present section. In it we show that the relation between 

 Convoluta and its green cells is both intricate and variable 

 in the sense that the nature of the relation changes as the 

 association becomes more intimate. 



We show that it is only by taking the widest view of the 

 case that it can be brought within the category of symbiotic 

 phenomena. 



The inquiry as to what is the significance and what are the 

 consequences of the association of green cells and Convoluta 

 resolves itself in large measure, but not entirely, into an 

 examination of the modes of nutrition of infecting alga and 

 of animal. The mode of nutrition of the infecting alga in its 

 free state must be first described. 



The fact that we have succeeded in obtaining luxuriant 

 cultures of the alga in artificial sea-water to which traces of 

 potassium nitrate were added proves that it is capable of a 

 typical plant-like (holophytic) mode of nutrition. The alga 

 under these conditions photosynthesises carbohydrates — 

 storing the surplus as starch — and utilises the nitrogen of 

 the nitrates in the formation of its proteids. 



VOL. 51, PART 2. — NEW SERIES. 16 



