CHAPTER V 



THE SIGNIFICANCE OF THE RELATION BETWEEN 

 COLOURED CELL- AND ANIMAL-CONSTITUENTS 

 OF THE PLANT-ANIMALS. 



WE have discovered enough already, with respect 

 to the relations which obtain between algal and animal 

 cells in our composite plant-animals, C. roscoffensis 

 and C. paradoxa, to convince ourselves that the re- 

 lation is not one of casual intimacy, lightly entered 

 upon and lightly abandoned ; but one which is of 

 fundamental importance to the animals. Before it 

 was realised how vital was this association, we 

 entertained hopes of raising a colourless race of 

 C. roscoffensis, and, having done so, of comparing 

 the colourless with the green adult, with the purpose 

 of ascertaining what changes had arisen in the 

 organism as the result of the symbiosis. Though 

 this hope has not been fulfilled, though it has proved 

 a task, if not impossible, yet beyond our powers, 

 nevertheless the attempts to accomplish it have 

 brought to light facts which show how ingrained in the 

 lives of the worms is this habit of association with 

 the algal cells of their respective infecting organisms. 



