THE GREEN CELLS OF CONVOLUTA EOSCOFFENSIS. 189 



swarm about ifc, to press in close ranks into the soft 

 gelatinous wall and so to imbed themselves in the envelope 

 (Hgs. G, 7; PL 13). 



We conclude that the eg'g-caj)sule exercises a chemotactic 

 influence on the active cells, and that the constant presence 

 of one or more green cells of the infecting alga on egg- 

 capsules contained in water to wliich a platinum loopful of 

 the active cells has been added is thus accounted for. The 

 behaviour of the cells wliich settle on the capsule proves that 

 they find this a favourable medium for growth. Within a 

 few hours each ceil, having v/itlidrawn its flagella, increases 

 considerably in size, and whilst retaining its green colour 

 takes on a granular appearance ; the eye-spot and pyrenoid 

 beconie fainter and the cell undergoes division. This division, 

 like that of the temporary resiing-cells already described, 

 is iu most cases longitudinal, but occasionally instances occur 

 in which the division is transverse. 



The mode of division is possibly determined by the state 

 of symmetry of the cell ; as long as the colourless proto- 

 plasmic plug occupies the cavity of the cup-shaped chromato- 

 phore the division will be longitudinal, but when the protoplasm 

 becomes distributed radially and uniformly transverse division 

 may occur, and this in turn may give place to the budding of 

 the spherical units of the palmella stage. 



The daughter-cells jDroduced by the division of the green 

 cells settled on the egg-capsule undergo a continuous series 

 of divisions, and so give rise to a loose colony, which colony 

 constitutes the green spherules, the discovery of which formed 

 the starting-point for this description. 



The second question, that of the systematic position of the 

 infecting organism, remains to be considered. The assem- 

 blage of characters presented by this alga — its firm wall_, its 

 single cup-shaped chromatophore containing in its hollow the 

 colourless protoplasm and nucleus, its pyrenoid and lateral 

 eye-spot far removed from the bases of the flagelia, its power 

 of starch-formation — indicate that it must be assigned to a 

 position in that primitive group of green alga) the Chlamydo- 



