214 | DR. Е. E. FRITSCH ON FRESHWATER АІС 
(h) SPHEROCYSTIS SCHROTERI, Chod., f. NIVALIS, F. Е. Fritsch. 
(РІ. 11. phot. 2, S.) 
In sample No. 3 of the yellow snow an organism (text-fig., F & С, p. 323) 
was very abundant which seems to be referable to the genus Spherocystis of 
Chodat *. This form consists of larger or smaller groups of round or oval 
cells (text-fig., F), green in colour and with granular contents, embedded in 
very soft mucilage, the outline of which is often irregular, but sometimes 
roughly circular (particularly in the case of the smaller colonies). The cells 
are separated by considerable intervals from one another, and mostly show 
а very uniform distribution (text-fig., F): the intervening mucilage 1s quite 
structureless and invisible. Each cell has a delicate bounding membrane 
of its own ; the shape of the cells is mostly spherical, but sometimes slightly 
oval, and a kind of colourless beak is often to be seen on one side. Ina few 
ases, especially after staining with iodine or gentian violet, it appeared as 
though there were a pair of short eilia arising from this beak and attached 
close together. All attempts to obtain clearer preparations were, however, 
unsuccessful, and the presence of cilia in the Antarctic form must therefore 
remain doubtful. I have been able to make out only very little of the cell- 
contents ; a small round body (probably a pyrenoid) can generally be 
detected, and there was commonly a small colourless area beneath the beak at 
the front end of the cell, but the chloroplast could not be properly deciphered. 
The cell-contents frequently contain starch, but fat was generall completely 
absent in these colonies.—4A part from the normal colonies just deseribed, two 
other kinds of colonies were observed. Firstly, such as showed wany or all 
of the cells in process of bipartition ; and, secondly, colonies in which most or 
all of. the cells had. their contents divided up into a considerable number of 
smaller cells (generally about eight). The latter have a very characteristic 
appearance (text-fig., G) and are, on the whole, commoner than the other two 
tvpes. The small cells in these colonies are often distinctly ovoid and pointed 
at one end. They are generally more or less filled with the all-pervading 
fat, which appears to arise in the cells of the normal colony at the time 
of their division ; for whereas the cells of the normal colony are, as above 
mentioned, quite devoid of fat, occasional colonies are to be found in which 
the cells contain considerable quantities of fat, and in these one or other of 
the cells are always in process of division. 
The genus Sphwrocystis was described by Chodat in 1897 (ef. footnote * on 
* Chodat, * Etudes de Biologie lacustre,” in Bull. Herbier Boissier, v. 1897, pp. 292-295, 
pl.9; also *Algues vertes de la Suisse, 1902, pp. 114-115, fig. 52. According to С, 5, 
West (Journ. Linn. Soc., Bot. xxxix. 1909, pp. 75, 76) Spherocystis Schroteri, Chod., and 
Tetraspora lacustris, Lemm., are synonymous (cf. also Chodat, Alg. vertes, p. 115). 
