COLLECTED IN THE SOUTH ORKNEYs. 303 
present in both kinds of cells, although certainly more abundant in the 
larger ones (figs. 2, 4, 5, 6). In a few cases the fat was apparently diffused 
rather equally throughout the contents of the cells, but it mostly formed very 
characteristic highly refractive lumps at one or more points immediately 
beneath the cell-wall. Frequently it appears in the form of concavo-convex 
lumps on one side of the cell, the mass of fat fitting like a cap over the 
protoplasmic contents (figs. 2, 6) ; occasionally this cap may even grow out 
of all proportion and give rise to a huge bulging mass on one side of the 
cell, which thus acquires an unusual shape. More rarely the fat forms 
a complete sheath with a rather irregular inner boundary around the proto- 
plasmic contents. Apart from the cases as yet described, in which the fat 
exhibits an obvious connection with the cell-contents, a number of cells were 
always to be found in which there were numerous rounded or oval lumps 
of fat completely segregated from the somewhat contracted protoplasm of the 
cell and lying in a more or less well-marked space between the latter and the 
cell-wall (figs. 4, 5). The cells concerned were always somewhat oval in 
shape and showed the pyrenoid and the characters of the chloroplast very 
prominently. In a few cases (fig. 5) two pyrenoids were visible through the 
drawn-out aperture in the chloroplast, and this seems to indicate that these 
oval cells were about to divide. On the whole, such cells contain a relatively 
smaller amount of fat than the ordinary spherical cells do, and it would thus 
appear as though this segregation and diminution in the amount of fat might 
precede cell-division. Some uncertainty, however, naturally attaches to this 
interpretation. until the aetual process of cell-division has been observed. 
The conclusion that the large spherical cells with their transparent mucilage- 
sheath and the groups of smaller cells belong to one and the same species 
may be challenged ; but apart from the identical structure of the cell in the 
two cases, I have found practically all transitions between the two sizes, and 
I think there can be little doubt that they all belong to the same species.— 
The genus Chlorosphwra * is characterised by its chloroplast and the power of 
vegetative division (which distinguishes it from the allied genus Chlorococcum), 
and by reproducing by subdivision of the cell-contents to form zoospores f; 
the absence of the latter method of reproduction in C. antarctica is not 
astonishing in view of the dormant character of the whole of the yellow 
snow flora. The new species seems to come nearest to C. angulosa 1, in 
which Artari states that reproduction principally takes place by vegetative 
* Chlorosphera is included by G. S. West (Brit. Freshwater Algz, p. 202) and some 
other authorities in the genus Pleurococcus, which is not in agreement with the views of 
Klebs, Artari, Wille, Oltmanns, ete. 
+ Klebs, “ Ub. d. Organisation einiger Flagellatengruppen, etc." in Unters, Bot, Inst. 
1881-86, p. 343; Artari, “ Unters. üb. Entwickl. u. Syst. einiger Protococcoideen," Diss. 
1892, p. 35. 
t Cf. Artari, loc, cit. p. 36, 
