202 F. KEEBLE AND F. W. GAMIJLE. 



auimal's tissues, but by tlie marked growth of the animal. 

 Whilst uninfected Convoluta, as described presently, remain 

 diminutive, those which become infected resume gi-owth and 

 increase rapidly in size. 



It appears probable on several grounds that the animal 

 cells are unable to lay hold of the starch contained in the 

 green cells. Thus, though young Convolutas fed on starch- 

 grains ingest them readily, they digest them not at all. 

 Again, when adult Convolutas are kept in darkness the starch 

 of the green cells disappears with extreme slowness — even 

 after eight days some starch may still be present. This 

 slowness of disappearance would seem to indicate that it 

 takes place according to the requirements of the green cell, 

 and not according to those of the animal. It is therefore 

 likely that the animal cells obtain the product of photo- 

 synthetic activity directly as sugar. Just as from the green 

 cells of a plant exposed to light there is a constant osmotic 

 streaming of photosynthesised sugar to the colourless cells, 

 so from the green cells of Convoluta sugar passes to the 

 colourless animal cells. In general, the demand in adult 

 Convolutas for food material is so great that but little starch 

 accumulates in the green cells. It is only during the mid- 

 day exposure to high light-intensity at the spring tides that 

 photosynthetic activity considerably exceeds that of trans- 

 location. At all other periods during the adult life of the 

 animal the photosynthesised carbohydrate passes away as fast 

 as it is formed from the green cell to the animal. The sugar 

 thus obtained is stored ultimately in the animal tissues or in 

 the eggs in the form of fat. 



We have next to consider the system, green cell and 

 animal, with respect to nitrogen metabolism. To do this 

 requires a review of the facts known with respect to the 

 nutrition of the constituents of the system. 



Von Graff (1905-1906) was the first to draw attention to 

 the absence of any vestiges of solid food from the body of 

 Convoluta. He concluded that this animal does not take up 

 solid food. Geddes' observations, Avhich, however, as we 



