390 
Gromia socialis, sp. nov. (PI. XX, figs. 7, 8, 9, 10, 11). 
Passing on from the freshwater rhizopods of the “ Radio- 
larian ” type, which have been the subject of the preceding 
pages, and in continuation of these casual notes of new or 
little-known forms which I have from time to time had the 
opportunity to meet with, I have now to draw attention to 
one of a different group which is amongst the most minute, 
hut one at the same time seemingly very well marked. Unlike 
some of those which have formed the subject of previous 
communications in the preceding pages, the present does not 
demand a new genus for its reception, as it falls, as will be 
seen, in my own opinion at least, as a new species under the 
genus Gromia (Duj.). 
Those, indeed, who are acquainted with the much larger 
representatives of the genus, such as even the comparatively 
small Gromia flumatilis, and conceiving that form magnified 
400 diameters, that is, to the scale of the accompanying drawings 
(PL XX, figs.7 — 1 1), being that to which all my previous figures 
have been made, might hardly be disposed to regard these 
two as strictly congeneric, or they might, on the other hand, 
regard the present as, perhaps, simply a young state of Gromia 
Jiuviatilis. But the present form has other and further re- 
semblances, to which I shall draw attention after having first 
given some account of it. Nay, this inert, at first glance 
nearly lifeless-looking, organism might almost be taken for 
some species belonging to the fungal genus Chytridium, and 
not as appertaining to animal life at all, only that it occurs 
free in the water, and not living parasitically (as w r ould a 
Chytridium) on some confervoid or other host. 
But if I was for a little somewhat puzzled by the Chy- 
tridium-like appearance of this form, rendered the more mis- 
leading by its occurring in the gathering chiefly amongst the 
branches of Microthamnion Kiitzingianwn (Nag.), a short 
examination soon dispelled that idea, and made it certain 
that I had indeed a true rhizopod before me. Amongst the 
ramifications of almost every example of this little alga in 
the gathering — never, indeed, in any way attached to them — 
— occurred this little rhizopod, either singly or in groups of 
two, three, four, five, six, or even more ; and it is sufficiently 
remarkable that I but seldom met with them in any other 
situation in the gathering at large ; so that whilst they lasted 
I presently found that the quickest way to meet with speci- 
mens was to look out for a plant of the Microthamnion, and 
then search with a “ quarter-inch ” amongst its branches for 
the little Gromia, which, however, owing to its minuteness, 
