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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 Euastrum margaritiferum move quite distinctly" (Bailey):—"Elles n'ont pas un mouvement sensible sur le porte-objet du microscope" (Brébisson)—contradictory assertions evidently. Mr. Archer (in Pritch. Inf., p. 5) says that "the Desmidieæ 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 currents in the water or disturbing influences beyond the field of the microscope 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 influences.

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 commencement of "swarming," quite faint at first; and when this had continued two or three minutes, I observed a slight oscillation of the frond. By degrees the oscillation increased, 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 crowd, 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 neighbourhood could 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)