in] GREEN CELLS OF CONVOLUTA 83 



solid food-substances. As old age comes on, it begins 

 to feed upon its green cells. Groups of such cells in 

 all stages of digestion and varying in colour from 

 yellowish-green to brown may be seen lying in large 

 vacuoles in the central digestive tissue of the bodies 

 of old specimens of C. roscoffensis. Thus, though, 

 as we shall see presently, the green cells of C. ros- 

 coffensis play an all-important part in the economy 

 of that organism, they are not the sole purveyors of 

 nourishment to it. Throughout a considerable part 

 of its life, C. roscoffensis is able to help itself to the 

 solid food supplied by the micro-flora and fauna of 

 its environment. 



Unlike C. roscoffensis, its ally, C. paradoxa, knows 

 no abstemious fits. Throughout its life it is a 

 glutton. A glance at the larval animal (Fig. 16) 

 gives the impression of a marine museum, so accom- 

 modating is the body of C. paradoxa. There, may 

 be seen the remains of several scores of diatoms of all 

 shapes and sizes. When examined immediately after 

 capture, a young or old C. paradoxa may be found to 

 contain, not only diatoms, but two or three Copepods, 

 each half as large as the animal itself, and, if it be late 

 in the summer, rows of tetraspores of red algse show 

 through the transparent body like so many cardinal 

 buttons. In C. paradoxa therefore, as in C. roscoffen- 

 sis, though the coloured, plant-like cells may well 

 play an important and even indispensable part in the 



(> 2 



