iv] GREEN CELLS OF CONVOLUTA 111 



C. roscoffensis in its more regular, oval shape and in 

 the possession of an eye-spot. Each green cell divides. 

 The daughter cells formed by the division lack the 

 oval shapes of the mother cell : they lack also eye- 

 spots. The colourless plug or neck of protoplasm no 

 longer occupies the position of a cork in a flask, but 

 lies eccentrically to the chloroplast and in it the 

 cell-nucleus is contained. In short, they are identical 

 with the green cells of the adult animal. Thus we 

 reach two conclusions of importance. First, that the / 

 green_cells of C. roscoflensis are preceded by colour- 

 less cells. Second, that thejnass o:f colourless proto- 2 

 plasm attached to the green cell is not, as Haberlandt 

 suggests, an animal cell standing in close relation 

 with a chloroplast, but is an integral part of the 

 green cell. As the young green cell continues to 

 divide, a significant change may be observed in the 

 shape and state of the nucleus. Distinct and spheri- 

 cal in the colourless and original green cells, it becomes, 

 in the cells produced by successive divisions, more 

 granular and indistinct, till, when the number of 

 green cells has increased considerably, some only 

 among them may be seen to contain nuclear material 

 fine granules in a clear area : the rest contain no 

 trace of nuclear material. In other words, the great 

 majority of the green cells of the adult animal are 

 not complete cells, but cells which show all stages 

 of diminishing nuclear substance (Fig. 17). Inasmuch 



