192 Snow. — Pseudo-Pleurococcus , Nov. gen. 
large radiating clusters were produced fully 1-2 mm. in 
diameter. A small one of these is shown in Fig. 16. 
The transformation from the filaments to the paren- 
chymatous masses began by longitudinal division taking 
place in the filaments (Fig. 13), when both longitudinal and 
transverse division continued until all semblance of a filament 
was lost. In *4°/ o Knop’s solution, if at any time during the 
transformation fresh nutritive solution, or even water, were 
added, the process was interrupted and new filaments were 
sent out from the rounded cells. In time these filaments 
also began to become parenchymatous ; but each time that 
fresh liquid was added filaments were produced, so that by 
adding liquid and then allowing the filaments to become 
parenchymatous, the shape and the nature of the develop- 
ment could, within certain limits, be controlled. 
Agar-cultures with little moisture seemed to reproduce 
best the conditions in nature. At first filaments were formed, 
but these soon passed into parenchymatous clusters of cells 
which afterwards became more or less disorganized ; the cells 
became rounded and the connexion became less intimate, so 
that, by disturbance, disintegration of the clusters occurred ; 
usually, however, two, four, or more cells remained united. 
The development can be traced from a single cell. If a cell 
from bark be placed in liquid it will develop directly into 
a filament (Figs. 7, 8). In a - 4°/ 0 Knop’s solution, however, 
a cell which had already become accustomed to this solution 
was seen to develop directly into a parenchymatous mass 
with a tendency to disintegration (Figs. 9-12), and one 
instance was noticed under similar conditions where cells 
separated directly after division, thus causing the Alga to 
remain in a unicellular condition. 
Strong nutritive solutions and also weaker solutions, pro- 
viding the Alga has existed in these for some time, produce 
the same effect as existence in the atmosphere ; that is, the 
parenchymatous and unicellular conditions occur, but change 
from the atmosphere to liquid always produces filaments. 
In general we can say that when the form exists in a medium 
