FRESHWATER ALG. 4) 
has recorded them for C. gigantea Dill, Wille (op. cit.) for C. marina (Duj.) 
Cohn, Chloromonas alpina Wille, ete. 
The spherical cysts bear an appreciable resemblance in size, thickness of wall and 
general character to a “forma cellulis plerumque globosis sed hine inde anguloso- 
globosis e mutua pressione” of Pleurococcus pachydermus Lagerh., described by 
Messrs. West (op. cit., p. 275), and, before their connection with Chlamydomonas 
subecaudata was noticed, I was for referring these cells to that form. The pyrenoids 
of this form of Pleurococcus pachydermus, however, appear to be circular and not 
angular, and the chloroplast is described as “ parietal” and “ of considerable extent” ; 
the wall is also thicker and more prominently stratified. It is therefore quite 
possible that the two forms bear no relation to one another, but of this I do 
not feel absolutely certain, the more as it is not quite apparent on what grounds 
the Wests refer their form to Plewrococeus pachydermus. Lagerheim’s original 
description and figures (“ Bidrag till kinnedomen om Stockholmstraktens Pediastréer, 
Protococcacéer och Palmellacéer,” Ofvers. af Kgl. Vet.-Ak. Férhandl., 1882, No. 2, 
pp. 78-79 and Tab. IIL, figs. 40-42) give no indication of a pyrenoid in the cells, 
and the membrane, though thick, is not stratified. The presence of a pyrenoid is 
of course a rather variable feature in the genus Plewrococcus, but the cells of Messrs. 
West’s form are certainly as much like the cysts of Chlamydomonas subcaudata as 
they are like Lagerheim’s figures of Pl. pachydermus. The processes sometimes 
developed on the cysts recall in some ways the process on Messrs. West’s forma 
stipitata, but those on the cysts have a much broader attachment and do not 
attain to nearly the length of those of the form described by the Wests. 
2. CHLAMYDOMONAS INTERMEDIA. 
(Pl. 1., figs. 15-18.) 
Chlamydomonas intermedia Chodat, Bull. Herbier Boissier, ii., p. 590, t. 22, 23; Wille, op. cit., p. 142, 
t. iv., fig. 15. 
Long. cell. = 10-13; lat. cell. = 6-8 p. 
Hlab.—Pond some distance behind hut, Cape Adare, January 9th, 1902. 
This species has also been found in material from a pond in the South 
Orkneys (Fritsch, op. cit., p. 324) and by Messrs. W. and G. 8. West (op. cit., 
p- 275) in Pony Lake. The first of the three samples from the pond at Cape 
Adare was almost a pure culture of this species, and exhibited a considerable 
degree of variation in the individuals. The pyrenoid, which was frequently 
angular, was generally situated in the posterior half of the cell (cf W. and G, 8. 
West, p. 275) and not in the middle. The nucleus lay just in front of the 
pyrenoid (7.c. in the middle of the cell, figs. 15, 17), sometimes directly adjacent to 
it (fig. 16), and was not uncommonly slightly shifted to one side of the cell (fig. 16) ; 
H 2 
