252 Transactions.— Botany. 
effort." Many observers have recorded notes on this subject. Ralfs quotes 
the following :—'* It was impossible to determine whether the vague motions 
of Closterium were voluntary or not" (Dalrymple) :—‘‘I have seen Euas- 
trum margaritiferum move quite distinctly” (Bailey):—** Elles n'ont pas 
un mouvement sensible sur le porte-objet du microscope” (Brébisson)— 
contradietory assertions evidently. Mr. Archer (in Pritch. Inf., p. 5) says 
that “the Desmidiee are seen to move. * * * * This phenomenon is 
most notable in Closterium; in others it is scarcely, in many not at all, 
cognizable.” The Rev. Mr. Osborne, in the Journ. of the Micros. Soc., ii., 
235, attributes the movements of Closteria to cilia, but no other observer 
seems to agree with his views. A friend of mine tells me that he has 
frequently seen Cl. lunula “rolling over and over.” But none of these 
statements appear to me to satisfactorily settle the question whether the 
Desmids do voluntarily travel, in any willed direction, as the Diatoms do, 
or whether the movements observed may not have been due to some cur- 
rents in the water or disturbing influences beyond the field of the miero- 
scope at the moment. I venture, therefore, to give a few notes of the 
motions observed by me in Cosmarium botrytis, motions which I believe 
to have been perfectly “voluntary,” and not due to any external in- 
fluences. 
I had been observing the plant on a morning during the present spring, 
and comparing it with some specimens in my English gatherings. The 
specimen under observation was situated in the centre of my “ field," in a 
small clear space between a dead Pinnularia and a small speck of dirt. It 
had been stationary for quite an hour, and there was no appearance during 
that time of any “ swarming” within it. The day was fine, and an even 
full light came through the diaphragm. All at once I detected a com- 
mencement of *swarming," quite faint at first; and when this had con- 
tinued two or three minutes, I observed a slight oscillation of the frond. 
By degrees the oscillation inereased, and the Desmid began clearly to move 
from its place. Soon the motion increased, and the plant steadily worked 
its way out between the Pinnularia and the dirt, not gliding straight-forward 
but jerking along, with a motion exactly like that of a man elbowing his 
way through a erowd, pushing forward first one side and then the other. 
It was clear that the Pinnularia could not produce any effect on it, as it 
was dead; and I carefully looked to see whether anything in its neigh- 
bourhood eould have set a current in motion, but found nothing. In about 
ten minutes the Cosmarium had jerked or elbowed itself out into the open 
water, and still continued its journey towards the apparent lower edge of the 
slide. Five minutes after, the “ swarming " somewhat increased, as did 
also the oscillation ; and the plant then stopped and began (also in jerks) 
