98 PLANT-ANIMALS [CH. 



cells. For the present, we content ourselves with 

 summing up what we have learned of the relations 

 between the animals and their plant-like cells. 



The coloured cells manufacture photosynthetically 

 food-materials, storing the surplus as starch or fat. 

 The animal receives from the coloured cells supplies 

 of food-material. So plentiful are these supplies in 

 C. roscoffensis that the animal comes, in course of 

 time, to rely altogether upon them for its nutrition. 

 Ceasing to take up food, it grows, bears eggs, and 

 produces young at the expense of the materials 

 supplied by its green cells. This life of curious 

 asceticism leads, however, to trouble. Though the 

 green cells continue to supply organic carbon com- 

 pounds, something or other is lacking from the 

 prepared food which the animal thus receives. To 

 make up for this lack, it digests in detail its green 

 cells, coming often in old age to present a strange 

 appearance head-end green, tail-end white. Hav- 

 ing exhausted its stores of green cells, without 

 apparently satisfying all its needs, it pines away 

 and dies. 



In its earlier youth, C. roscofFensis feeds, after the 

 manner of animals in general, on other plants or 

 animals. This is the first phase. In the course thereof, 

 green cells appear in the body, increase, multiply, 

 photosynthesise and distribute food materials to the 

 animal's tissues. For a while, C. roscofiensis receives 



