204 F. KEEBLE AND F. W. GAMBLE. 



that we attribate tlie failure of all our attempts to raise a 

 colourless race of Convolutas. 



The infected young animals continue during the period of 

 development of their green cells to ingest solid food. But 

 when this period is complete and the reproductive organs are 

 mature all ingestion of solid food ceases. 



The only food materials now available are such substances 

 synthesised by the green cells as may pass in solution from 

 green cell to animal cell. 



This mode of nutrition of the animal is of short duration. 

 It is soon succeeded, or rather overlapped, by another which 

 consists in the digestion by the animal cells of whole groups 

 of green cells. During the adult life of Convoluta large or 

 small aggregates of green cells in all stages of disintegration 

 are to be met with, lying in vacuoles in the axial tissue which 

 constitutes the gut of the animal. 



From this stage onward the ultimate significance of the 

 relation between animal and green cells stands more and 

 more clearly revealed. The animal is now and henceforth 

 parasitic on its green cells. As a result of this habit old 

 animals are not infrequently to be met with in laboratory 

 cultures whose bodies are half green and half colourless. 



If in order to summarise these conclusions we employ the 

 terms used by plant physiologists in describing the principal 

 modes of nutrition, and if we consider for this purpose a 

 green Convoluta as an organism, then we may distinguish 

 the following styles of nutrition : 



(1) In the pre-infection stage the animal feeds hetero- 

 trophic ally — i. e. typically animal- wise. 



(2) Young infected stage; the green animal is nourished 

 mixotrophically, viz. by (solid) ingested food, and by 

 photosynthesised food-substances. 



(3) Mature green Convoluta; the mode of nutrition is 

 holophytic — typically plant-like. The green cells are the 

 photosynthetic agents, the animal's colourless cells receiving, 

 just as do the colourless cells of plants, the products of 

 photosynthetic activity. 



