FRESHWATER ALG^E. 9 



has recorded them for C. gigantea Dill, Wille (op. cit.} for C. marina (Duj.) 

 Cohn, Cldoromonas alpina Wille, etc. 



The spherical cysts bear an appreciable resemblance in size, thickness of wall and 

 general character to a " forma cellulis plerumque globosis sed hinc inde anguloso- 

 globosis e mutua pressione" of Pleurococcus pachydermus Lagerh., described by 

 Messrs. West (op. cit., p. 275), and, before their connection with Cklamydomonas 

 subcaudata 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 Pleurococcus pachydermus. Lagerheim's original 

 description and figures (" Bidrag till kiinnedomen om Stockholmstraktens Pediastreer, 

 Protococcaceer och Palmellaceer," Ofvers. af Kgl. Vet.-Ak. Forhandl., 1882, No. 2, 

 pp. 78-79 and Tab. III., 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 Pleurococcus, 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 PI. 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 L, 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. = 10-1 3 p.; lat. cell. = 6-8 p.. 



Hob. 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. S. 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. S. 

 West, p. 275) and not in the middle. The nucleus lay just in front of the 

 pyrenoid (i.e. 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 



