193 
Snow. — P sen do -P leuro coccus, Nov. gen. 
where there is little moisture, the P leurococcus-Yike condition is 
produced, the cells being either single or in small clusters ; 
but when subjected to much moisture filaments are produced. 
This would seem to hold true also in nature, for even among 
the parenchymatous masses of cells taken from bark the form 
of the masses often suggested filaments, which had possibly 
been produced during a wet period, and afterwards trans- 
formed to the parenchymatous condition during a following 
dry season. 
Whether we can regard this as a degenerate form of Alga 
which reverts to a filamentous form when placed in liquid 
media, is difficult to say. Might we not with equal right 
regard the filaments as a higher form which is being evolved 
from the lower by being placed under more favourable 
conditions ? 
Pseudo-Pleurococcus VULGARIS, Nov. sp. 
This form is characterized in its aerial existence by smaller 
cell-complexes than the preceding species, and in liquid 
media by branching less profusely (Figs. 17, 18). The mode 
of branching also is different. Instead of branches arising 
from any cell along the filament, their origin is terminal, two 
growing-points being developed at the apical cell. 
The chromatophore does not occupy the whole cell, but 
lines only a portion of the cell-wall ; and in the filamentous 
form often more than one chromatophore is present. The 
single cells are 6*5 [jl in diameter ; a pyrenoid is present ; 
no blue colour was produced in the membrane either with 
chlor-iodide of zinc or with iodine and sulphuric acid. 
The conditions governing form in this species are the same 
as in the preceding. In liquid culture-media filaments were 
produced, while on agar with Knop’s solution total disinte- 
gration took place. The transformation from the filamentous 
to the unicellular condition also began by longitudinal division 
occurring in the filaments (Fig. 19). The process of disin- 
tegration, however, took place more rapidly and was carried 
farther than in the first species, for, within three weeks' time, 
