. The Canadian journal of industry, science and art. 326 ON THE MOVEMENTS OF THE DIATOMACE^.. and the thin glass cover of the live box. After a very short period of rest, the Pinnularia gave one or two short jerking motions, and then the Cocconema began to move rapidly, broadside on, in a direction opposite to that pursued by the former (vphich remained sta- tionary) until it passed partly beyond it, when the Pinnularia resumed its journey ; this vras done twice in precisely the same manner ; on the third journey, it had changed its course, and passed beyond the ob- structing valve. The arrow
. The Canadian journal of industry, science and art. 326 ON THE MOVEMENTS OF THE DIATOMACE^.. and the thin glass cover of the live box. After a very short period of rest, the Pinnularia gave one or two short jerking motions, and then the Cocconema began to move rapidly, broadside on, in a direction opposite to that pursued by the former (vphich remained sta- tionary) until it passed partly beyond it, when the Pinnularia resumed its journey ; this vras done twice in precisely the same manner ; on the third journey, it had changed its course, and passed beyond the ob- structing valve. The arrow indicates the direction in which the Pinnularia was moving. The Cocconema was of course forced in the opposite direction. Now, a result very similar to these might be produced by the expulsion of a fluid from the Diatom valve, according to Professor Smith's theory, but the orifices through which it would require to be forced would have to be placed along the side of the valve as well as at either end. And not only would this be necessary, but two sets of orifices, pointed in opposite directions, would be essential, in order to produce the double motion, backwards and forwards. While two sets more would be required to produce the motion I have before described, when the diatom saw fit to change its course. And besides all this elaborate mechanism, another must still be added, by means of which every opening would be completely closed but those for the moment employed in producing the motion in one given direction. If this really is the correct solution of the question, the motion then of the Diatomacese is unique, for I doubt if any thing anala- gous to it can be found in nature. But if the presence of cilia be granted them, then there is no difiiculty in at once understanding how every movement of the diatom valve can be readily produced merely by changing the direction of the ciliary motion. The objection urged by Professor Smith, that by colouring the water, no motion in the
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