94 PLANT-ANIMALS [CH. 



The phase in the relation between coloured, 

 chlorophyll-containing cells and animal tissues which 

 we have just described, presents the closest parallel 

 with the relation which obtains between the green 

 and non-green cells of any chlorophyllous plant. 

 In both plant and plant-animals, the chlorophyll- 

 containing cells manufacture carbohydrates in excess 

 of their own requirements, and, in both, the excess is 

 translocated to the colourless tissues and used by 

 them as food-material. 



But, in certain circumstances, C. paradoxa and, 

 to a somewhat less degree, C. roscoffensis may exploit 

 their coloured cells in a more summary manner. 



Thus, when animals are kept in darkness in sea- 

 water filtered through a Pasteur-Chamberland filter 

 they become reduced greatly in size. The reduction 

 in size is, as we know, greater, and takes place more 

 rapidly, in dark-kept than in light-kept animals. 

 In one experiment in which the animals were 

 measured, those which had been kept in darkness 

 were, on the average, two and a half times as small 

 as those which had been kept in the light; the 

 average superficial dimensions of the dark-kept 

 C. paradoxa being "08 square inch and those of 

 the light-kept animals *2 square inch. 



The powers of resistance to starvation of both 

 C. roscoffensis and C. paradoxa are extraordinary. 

 Thus, it is possible to maintain C. paradoxa alive for 



