112 PLANT- ANIMALS [CH. 



as it is a well-established fact that the nuclear part 

 of the protoplasm plays an important role in the 

 life and work of the cell, these observations throw 

 light on the subordination of the green-celled tissue of 

 C. roscoffensis to that of the animal. Since, also, the 

 nucleus is known to play a part in cell-wall formation, 

 we are no longer surprised that a cell- wall fails to 

 form in the green cells. Further, in this progressive 

 nuclear degeneration, we have the explanation of the 

 inability of the green cells to survive separation from 

 the tissues of the animal. Those green cells whose 

 nuclei are least degenerate are capable of division, 

 but even they have suffered. They are no longer 

 able to form a cell-wall nor to exist as independent 

 organisms. As division succeeds division, the nuclear 

 material becomes further reduced till, in the adult 

 animal, it is often difficult to find any sign of nucleus 

 in the large majority of the green cells. 



It is highly probable that the advent of this 

 enucleate stage in the green cells is the signal to 

 the animal to devour them. Though still capable 

 of photosynthesising, the green cells, unable to offer 

 resistance to those of the animal, are surrounded by 

 the latter, devoured and digested. A significant 

 phenomenon is revealed by the drawings (Fig. 17) of 

 sections through the green cells of C. roscoffensis. 

 In places, ingrowing rows of cells may be seen budded 

 off from the outermost green cell and, of these rows, 



