280 The Botanical Gazette. [July, 
cells. The cells are situated in the periphery of the sphere, 
of which the gonidia occupy a hemisphere or more and the 
vegetative cells the remainder. The centers of the two areas 
thus distinguished coincide with the ends of the long diame- 
ter in ellipsoidal specimens. The vegetative cells are about 
12 in diameter, and the gonidia just before division 25-30. 
Each vegetative cell (in young individuals the cells are all 
alike) is oval, with the smaller, clearer end directed outward, 
and bearing two cilia which project through the gelatinous 
envelope. In each cell a pyrenoid and a red pigment cor- 
puscle are conspicuous, the latter situated on the surface near 
the forward or outer end (figs. 5 and 7). The pyrenoid is in 
the inner end of the cell and appears to lie within the center 
of the single chromatophore, the edges of which extend for- 
ward around the periphery of the cell. Specimens fixed with 
1% chromic acid, washed, stained with hematoxylin and after- 
-ward with alum cochineal, show in each cell a centrally 
located nucleus with a well defined nucleolus (figs. 7 and 8). 
Some young specimens fixed with picro-nigrosin show a vacu- 
ole in the hyaline forward end of the cell. ; 
A number of specimens were fixed and stained with a view 
to ascertaining whether any protoplasmic connection exists 
between the cells. After fixing on the slide with 1% chrom- 
ic acid, some were stained with safranin, Bismark brown, 
alum cochineal and haematoxylin. Others were fixed and 
stained with picro-nigrosin, but in no case did any connect 
ing threads appear. At the time when these observations 
were being made, the writer met with a specimen of Volver 
minor Stein, and here the connecting threads between a 
cells were visible in the living plant under a magnification 
only 57 diameters and without the use of any stain. In the 
young of Pleodorina the cells are all of the same size and 4P- 
parently alike, but in the older ones the gonidial cells be- 
come gradually larger, and then more spherical an é 
even Slightly flattened. The granular cell-contents increas® 
the pyrenoids increase in number, and the red pigment nee 
puscle becomes less conspicuous and disappears. sl 
The movement of the plant in the water was followe' ia 
the case of a few individuals bearing well developed gom! : iv 
In swimming through the water the vegetative pole is pare 
forward and the plant revolves to the right (in observed re 
' on the axis connecting the vegetative and reproductive po 
