196 F. KEEBLE AND F. W. GAMBLE. 



each of tliroe gi*aiinles. Ro fnr Ave liavo mot witli no indica- 

 tions of mitotic division except this separation of the nuclens 

 into rows of g-vanules. 



In the division stages of the non-motile cells, gronps of 

 rods and grannies may be made ont and appear to represent 

 phases of nuclear division. 



The cells of the colonial stage (Fig. 15, pi. 14) present two 

 types of nncleus. The resting nucleus, lying slung in cyto- 

 plasm in the centre of the cell, consists of a homogeneous, 

 deeply-staining central body, surrounded by a clear area, 

 the limits of which cannot be sharpl}^ distinguished from 

 those of the cytoplasmic envelope containing it. The dividing 

 nucleus consists of a diffuse group of fine granules, occupying 

 a circular or oval area of the cytoplasm. The grannies 

 sometimes form two groups at opposed ends of a cell. 



Thus the nuclei of the flagellated stage and of the actively 

 developiug palmella stage are, though small, distinct and 

 readily recognisable. So, too, is the nucleus of the green or 

 colourless cell, as it lies in the body of a larval Convolut.i 

 immediatel}^ after ingestion. After the first division in the 

 body the nucleus of each daughter-cell has the appearance of 

 that just described as characteristic of the actively dividing 

 cells of the colonial stage — namely of an oval area occupied 

 by diifuse granules (Fig. 13, pi. 14). As division of the 

 infecting cells proceeds the presence of nuclear grannies in 

 the resultant cells is made out with increasing dilHculty, till 

 finally, in the adult animal, whoso body is densely jiacked 

 with green cells, it is often difficult to pick out any in which 

 remnants of nuclear grannies remain. The great majority of 

 the gi-een cells of Convoluta are not complete cells, but cells 

 which show all stages of diminishing nuclear substance 

 (Figs. 9 and 10, pi. 13). Thus the conclusion to which our 

 physiological investigations led us that the body of Convoluta 

 is the grave of the green cell receives liistological confirmation. 

 If this degeneration of the nucleus begins almost immediately 

 after the ingestion of the infecting cells some light is pei-haps 

 thrown on the fact to which attention has frequently been 



