324 ON THE MOVEMENTS OF THE DIATOMACESR. 
ON THE MOVEMENTS OF THE DIATOMACE 
BY PATRICK FREELAND, ESQ. 
Read before the Canadian Institute, January 19th, 1861. 
The producing cause of the movements of most of the free species 
of the Diatomacez has never yet been satisfactorily ascertained, not- 
withstanding the amount of attention bestowed upon the subject. 
Many eminent observers, with Ehrenberg at their head, maintain that 
the motion is owing to the action of cilia. ‘‘In some species of the 
Naviculez,” he says, “it is produced by a flat snail-like foot protruded 
from each end of the valve.” Others, again, maintain that it is owing 
to forces operating within the frustule, and connected with the 
endosmotic and exosmotic action of the cell—the fluids which are 
concerned in these actions entering and being emitted through 
minute foramina at the extremities of the valves. Dr. Smith, who 
maintains the movement to be of merely a mechanical nature, pro- 
duced by a force not depending upon any act of volition in the 
living organisms, in his Synopsis of the British Diatomacez, says, 
‘it appears certain that these motions do mo¢ arise from any external 
organs of motion. The more accurate instruments now in the hands 
of the observer have enabled him confidently to affirm that all state- 
ments resting upon the revelations of imperfect object-glasses, which 
have assigned motile cilia or feet to the Diatomaceous frustule, have 
been founded upon illusion or mistake. Among the hundreds of 
species (Dr. S. continues) which I have examined, in every stage of 
growth and phase of movement, aided by glasses which have never 
been surpassed for clearness and definition, I have never been able to 
detect any semblance of a motile organ; nor have I, by colouring the 
fluid with carmine or indigo been able to detect by the particles sur- 
rounding the diatom, those rotatory movements which indicate in the 
various species of true infusorial animalcules the presence of cilia.” 
In a paper on this subject, read before the London Microscopical 
Society, in 1855, by Mr. Hogg, he says, “ I have repeatedly satisfied 
myself that their motive power is derived from cilia arranged around 
openings at either end—some around central openings, which, with 
those cilia at the ends, act as paddles or propellers.” 
