397 
Gromia, for instance, from both of which, indeed, our form 
upon other characters is sufficiently and distinctly removed. 
Perhaps, however, I err in ascribing any particular import- 
ance to such an organization in our form, but, at least, such 
is one of its characters. In the drawing (PI. XX, fig. 6) I 
have tiied to depict the pulsating vacuole at its extreme point 
of distension just before its discharge and collapse in that 
wrinkled and contracted manner with which every one who 
has seen the same phenomenon in Actinophrys or in Actino- 
sphserium must be familiar. 
The body-mass of our form is rather densely granular, and 
thereby rendered somewhat opaque. Immersed in the sub- 
stance can be seen, without much trouble, however, a large 
and globular body, the so-called nucleus. With a little pains 
this can be pressed out intact, and is seen to be of that gra- 
nular character and somewhat bluish hue of the similar body 
in an Amoeba, the body substance bearing opaque, somewTiat 
coarse, and crude-looking granules. 
Having thus endeavoured to convey an idea of this new 
form, I shall below contrast it with those few which seem to 
come nearest it, or for which it might be mistaken, and 
thereby, perhaps, overlooked, even though it should be 
encountered elsewhere by other observers. I need hardly 
say, however, that the fringe-like emanation of pseudopodal 
processes in conjunction with the anterior, long, and branched 
ones, would alone seem enough to distinguish the present form 
from any other. I have thought that the generic name 
Diaphoropodon calculated to express this speciality, and name 
this curious form accordingly Diaphoropodon mobile, reserving 
short generic characters for the present. The resemblances 
wdiich this form presents are, of course, apart from the circum- 
stance alluded to. Leaving, then, the body processes out of 
view r , the most immediate allies of our Diaphoropodon are 
seemingly forms which appear to appertain to Pleurophrys 
(Clap, et Lachm.), represented by the three drawings (PI. XX, 
figs. 1, 2, 3), and Amphitrema (nov. gen., PI. XX, figs. 4, 5), 
to Avhich I would briefly advert in the next following 
section of the present communication. 
Notes on Certain Fresh-water Species of Diatomace-e. 
By A. S. Donkin, M.D. 
The late Professor Smith, in referring to the genus Epi- 
themia in his ‘Synopsis of the British Diatomaceae ’ (vol. i, 
p. 11), observes that “ this genus, as its name implies, is 
