
THE MOTION OF DIATOMS. 179 

cases where extraneous matter is seen adhering to, or trailing after 
a diatom, how do we know that the adhesive property does not 
reside in the adhering matter and not in the diatom at all? I 
have often seen such masses of flocculent matter adhere to entomo- 
straca and rotatoria when they happen to brush against it, and 
remain attached some time until detached by the violence of their 
movements. 
The remarkable alternation of motion seems to me a very strong 
objection to the ciliary theory, and equally so to that of the pre- 
hensile filaments. No other ciliated or flagellate organism that I 
know of exhibits such alternation, but whether animal or vegetable, 
when free to move they swim hither and yon in a purposeless and 
indefinite course, without limit. But if prehensile filaments exist, 
they should, to be in accord with other provisions of nature, bear 
a relative proportion in size to the diatom by which they are 
borne. Yet, in large diatoms, like Amphiprora ornata, Surirella 
splendida, S. turgida, etc., when active and moving with great force, 
no trace of cilia, pseudopodia, filaments, or anything of the kind 
has yet been discovered. I have watched a large thick Sws7rella 
plowing its way through tangled masses of Zadellarta, and sweep- 
ing before it masses larger than its own bulk, and hoped to find 
some trace of the means by which the resistless motion was im- 
parted, but without success, although I brought to the task objec- 
tives capable of resolving the Amphipleura pellucida. No trace of 
currents, of cilia, or any external appendages could be seen, nor 
any motion in the endochrome of the diatom. I have also 
observed that these large diatoms do not show the same attrac- 
tion towards loose particles in the water which the smaller ones 
do. 
I have seen living diatoms, both still and moving forms, with a 
substance adhering to them which had exactly the appearance of a 
fragment of an amceba, but without the movement natural to the 
latter. And I have seen the same substance adhering to dead 
diatoms entirely free from endochrome. In all cases I am con- 
vinced it was foreign to the diatom and had no connection with 
the motion of the diatom to which it adhered. 
Most diatoms, even when unobstructed, move with a quiveritty 
or staggering motion, much like a drunken man, which does not 
seem consistent with ciliary action, or with currents produced by 
osmotic action; and, besides, we should expect the currents pro- 
duced by cilia or any other force capable of moving the diatom, to 
be strong enough to move adjacent particles when the diatom 1s 
held fast. Yet we do not see free particles moved, or any evidence 
of current in the water, except where there is contact with the 
diatom, Frequently we see a small mass moving along the diatom 
while another mass, apparently in contact with it, 1s not affected 
