143 
Protophyte from Ceylon. 
mucilage has been used by some authors to distinguish between Dictyo- 
sphaerium on the one hand and Westclla and Dimorphococcas on the 
other (4). West (5) even divides the Dictyosphaeriaceae into two tribes 
on the basis of this character. Observations on the mucilage-sheath of 
D. Fritschii show that it has the same nature as that described by Senn 
for Dictyosphaerium piilchellum , Wood, each partial colony having its own 
mass of mucilage, as will be seen in our figure. The latter should be com¬ 
pared with that given by Senn (3). Incidentally it may be noted that the 
radial striations shown so prominently in some copies of Senifis figure are 
delicate structures which can only be seen on staining with Bismarck brown, 
and are invisible in the unstained condition. It is clear that the absence of 
a gelatinous sheath cannot be used as a generic distinction for Dimorpho- 
coccics , the essential feature of the latter genus being, of course, the 
dimorphism of the cells. 
The partial colonies always consist of four cells each. As in the 
other species of Dimorphococcus , the members of each group were arranged 
in a manner comparable with the arrangement of the petals in a tetra- 
merous corolla. D. Fritschii differs from D. lunatics , A. Br., in the fact that 
each cell has its bwn distinct stalk. In this respect it agrees with D. corda- 
tus, Wolle, and to some extent with the species of Dictyosphaerium. The 
mucilage stalks of D. Fritschii are much thinner than those of D. cordatus , 
as figured by Chodat (2), but agree with the original of Wolle (6). They 
are shorter than in any Dictyosphaerium. The very peculiar thickening or 
lappet usually to be observed at the base of each cell, i. e. at the point where 
the stalk is attached, is a remarkable distinguishing feature of our species. 
It does not appear to be a mere thickening of the cell membrane, but rather 
a small segment of the mother-cell wall which has not been used up in the 
formation of the stalk. 
In 1897 Bohlin (1) described the development of the colonies of 
Dimorphococcus lunatics, A. Br. He discovered that the gelatinous threads 
which hold the cells together are only the remains of the older membranes. 
Thus the colonies show a certain morphological resemblance to those of 
Dictyosphaerium. In the latter genus, however, the wall of the mother-cell 
splits into four pieces when the cell divides into four, each piece remaining 
attached to one of the daughter cells. In Dimorphococcus lunatics , A. Br., 
the daughter cells are adpressed together in tetrads ; it is therefore not 
necessary here for each cell to have its special piece of the parent mem¬ 
brane, and the splitting is suppressed. Further, the walls of' the mother and 
daughter cells do not fuse with one another, and the daughter tetrads are only 
fixed to the remains of the mother-cell membrane by partial gelatinization. 
Bohlin does not believe that the similarity between Dimorphococcus and 
Dictyosphaerium indicates a near relationship between them. He points out 
that Zopf has shown certain morphological similarities to exist between 
