IN YEGETABLE BIOLOGY. 375 
breaking away from the zoosporangium ; indeed, canobia-bearing 
zoosporangia were kept for a week in watch-glasses in the hopes 
of their yielding motile ecnobia, but in all cases without success; 
moreover, failure became more apparent day by day as theamount 
of gelatinous matter increased, and the ccenobial wall, and espe- 
cially the cilia, got more and more entangled. Now under 
natural eonditions this gelatinization is kept more in abeyance; 
and I feel convinced that the cenobia do not experience this 
difficulty in making their escape when in their native habitat, 
aided, as they must be, by currents in the water produced by 
wiuds and by the swaying of plants, as well as by movements of 
aquatic creatures, to say nothing of the friction of Cladophora 
threads one against the other. Unfortunately these are condi- 
tions impossible of artificial production. The Palmella, Gleo- 
cystis, and Botryocystis states are, however, less susceptible; for I 
have succeeded in keeping them alive and apparently quite 
healthy for upwards of a week, even underneath a cover-slip, by 
frequently renewing the water, and preventing its evaporation 
by placing the slide under a bell-glass. 
One very curious point is that, when in the fixed state, the cilia 
do not move. I attended carefully to this; but was never able 
to distinguish ciliary motion apart from external disturbance, as 
in running in fresh water under the slide &e. Even the cilia of 
the coenobia of figs. 15 and 25, c, were motionless, apparently for 
the same reason that the coenobia themselves were so, viz. en- 
tanglement in gelatinous matter. This will not aecount for 
quiescence in other cases, e. g. a young unicellular zoosporan- 
gium with undifferentiated wall: here we must suppose that the 
power to move has been lost; and this is just what would be 
expected, since movements, even of the most violent kind, would 
obviously be useless in view of the firm adhesion contracted 
between the Cladophora and its messmate. Still the fact is some- 
what remarkable, seeing that in almost all the phyla of the animal 
kingdom stationary cells with motile cilia are of constant occur- 
rence. How it is that the cilia of the free coenobia are enabled 
to move, I cannot say: possibly the introduction of fresh water 
into the zoosporangium and dissolution of the zoosporangial 
wall may relieve the cilia of an embargo upon their movement 
consequent on their passage of the thick wall, the seat of move- 
ment residing near their closely invested base; but this is mere 
conjecture. 
