THE GREEN CELLS OF CONVOLUTA ROSCOFFENSIS. 195 



nnique among the many thousands examined — lends support 

 to the view which we put foi'wai'd that the " Convoluta stage" 

 of the alga is to be regarded as consisting of an hypertrophied, 

 senescent palmella. 



The animal in question presented an appearance under the 

 low power of the microscope very like that of a fern-pro- 

 thallus. Its body was lobed posteriorly, so as to present a 

 conventionally heart-shaped form, and its green cells, so 

 closely packed as to obscure all other elements of the body, 

 were I'ounded and uniformly green, quite like those of the 

 typical palmella-stage, which stage at the time of these 

 observations was unknown to us. 



To return to our consideration of the green cells of the 

 normal animal. The rapid division of the green cells in 

 recently infected Convoluta is accompanied by significant 

 changes in the nucleus, changes which since they render 

 intelligible the loss of power of independent existence on the 

 part of the green cells of the adult animal we now describe in 

 some detail. 



The nucleus of the flagellated cell (fig. 12, PI. 14) lies in the 

 colourless part of the protoplast, about the middle of its depth, 

 equidistant from the bases of the flagella and the pyrenoid. 

 Its general appearance is that of a spherical uniformly staining 

 body, from the periphery of which radiating branches run, 

 two upward towards the points of insertion of the cilia and 

 two downward toward the pyrenoid. These branches, though 

 mainly cytoplasmic, show by their staining reactions with 

 nuclear stains (e.g Benda's iron life matoxylin) that they also 

 contain nuclear material. 



In other flagellated cells the nucleus presents the appear- 

 ance described by Dangeard (1899) as occurring occasionally 

 in the Chlamydomonadefe, of a clear spherical area, in the 

 centre of which lies a deeply staining " nucleolus." Agaiu, in 

 other specimens the nuclear substance consists of three fairly 

 large granules lying either side by side or else pyramid-wise j 

 the granules may be spherical or elongated, of equal or 

 unequal size. Occasionally specimens show two vertical rows. 



