306 DR. Е. E. FRITSCH ON FRESHWATER ALGJE 
and a cap of fat at each end of the cell-cavity ; commonly these two caps of 
fat are roughly equal in size and more or less concavo-convex in shape, the 
concave side having an irregular outline and being directed towards the 
granular protoplasm in the centre of the cell. In other individuals two 
additional lumps of fat on either side of the cell occurred together with the 
other two masses. In some individuals, finally, the whole of the protoplasm 
was obscured by the fat, such cells presenting an opaque yellowish-white and 
homogeneous appearance. 
Owing to the very marked similarity of the cell-contents in Scotiella 
antarctica and Chlorosphera antarcticu, I was at one time inclined to regard 
the large isolated cells of the latter as resting-stages of the Seotiella. This 
view seemed to obtain additional support from the fact that now and again 
an individual of S. antarctica is io be found in which the contents appear 
rounded off (fig. 16) and look very similar to a large Chlorosphera-cell 
(except for the absence of the mueilage-envelope). There is, however, a 
good deal that negatives such an assumption. In the first place, it 
would appear as though the Scotiella forms resting-cells of a rather different 
type (cf. fig. 15 and the subsequent description). There is further an absence 
of connecting-stages between the normal Seotiella-individual and the Chloro- 
sphera-cells (saving such a stage as is shown in fig. 16). And, lastly, the 
Chlorosphera-cells, as above mentioned, are of very diverse dimensions, 
whereas the range of size of the Seotiella-individuals is small; and I have 
never met with any small enough to give rise to resting-cells of the 
dimensions found in the smaller Chlorosphvra-cells. The cells of the latter 
(even the largest) are, moreover, occasionally found in considerable masses 
(twenty to fifty or more), separated from one another only by their mucilage- 
envelopes, which then often become polygonal as a result of mutual pressure ; 
this is much more like what we should expect in а Chlorosphera than in 
resting-cells of a form like the Scotiella, occurring as it does as isolated 
individuals. My object in discussing this point in detail has been to avoid 
the immediate adoption of an assumption which at first sight seems very 
plausible. At the same time, I do not wish to deny that with only the 
present material available for investigation we cannot completely dismiss the 
possibility of certain of the larger Chlorosphira-cells ultimately proving to 
belong to the life-cycle of Scotiella antarctica * ; it does not, however, seem 
probable. 
In the course of the previous paragraph reference was made to resting- 
cells of Scotiella, which appear to arise in the following way (Pl. 10. 
figs. 12-15) :—Rather rarely one finds individuals of this Alga in which the 
contents are markedly contracted or more or less rounded off (figs. 12, 13, 
* If so, they might prove to be germination-stages of the resting-cells described in the 
next paragraph, but there is no evidence for this. 
