Monthly Mi ical Ve y 
Ceo Notes on Diatomacee, 33 
a 
VI.—Notes on Diatomacez. 
By Professor ArtHuR Mrap Epwarps. 
(Continued from p. 250, No. X VIT.) 
Atone with the Bacillaria in the brackish water at Hoboken, I 
found numerous individuals of an Amphora, which I have known | 
in this neighbourhood for many years, and which I considered un- 
named as yet. ‘To it I have given the provisional name of A. lan- 
ceolata, on account of the form of its outline. This genus has 
always been considered an epiphytaceous one; that is to say, one 
which grows attached to other plants or submerged substances; yet 
this form was free and in active motion. In fact I think it was 
one of the most lively diatoms I ever saw. So another smaller 
species of Amphora which is common near here, is always, as far 
as I have noticed, free. Here we have species appearing both in 
the free and attached conditions, and this is even more strikingly 
illustrated in Schizonema. 
Bacillaria paradowa is usually set down as the most rapid in 
motion of the Diatomacez, its velocity beg recorded by Smith, as 
he measured it, at over one two hundredth of an inch in a second. 
This is certainly pretty quick when we consider that the length of 
the frustule is only *0025 of an inch. But my experience has been 
that its velocity varies in every degree from that mentioned to per- 
fect rest ; at times some individuals will be in rapid movement, while 
others are motionless; and also I have remarked that from sunrise 
to noon seems to be the period during which, under ordinary con- 
ditions, the movement is most active, while during the afternoon it 
is very sluggish, and at night almost nal. This Amphora, as I saw 
it at the time mentioned, was moving even more rapidly than I 
ever saw a bacillaria move, and that with a steady onward pro- 
gression very different from that of most naviculiform diatoms, 
It appears to me that in Schizonema and similar genera, which 
consist of silicious loricated naviculiform frustules enclosed in mem- 
branous tubes, as soon as a rupture of the investing membrane takes 
place, by fracture or tearing asunder, almost immediately a know- 
ledge of the fact 1s in some way communicated from the point at 
which the opening occurs to all other points of the tube, as at once 
the contained frustules which hitherto have been at perfect rest, or, 
at most, only moving to a very slight extent, and even then in an 
extremely sluggish manner, become animated in their motion, and 
the most of them move towards, and attempt to escape from, the 
opening made. And this evidently does not result, as might at first 
have been supposed, from any pressure exerted upon them from the 
closed end of the tube, and which, therefore, only shows itself when 
VOL. IV. D 
