251 
and this strikes me, indeed, so forcibly that I, for my part, 
cannot at all coincide with those who hold the view that 
there is no fixity or definiteness amongst these beings, and 
that all the varied forms — some more, some less abundant — 
which present themselves are but simply phases of one and 
the same protean rhizopod. 
Such being the views which an at first casual, and after- 
wards more special, examination of these beings had impressed 
upon me, I naturally began to think it probable that the 
types of rhizopods of the fresh waters might not be altogether 
confined to the ordinary ones already recorded in books, 
represented by the genera Difflugia and Arcella, Euglypha, 
Cyphoderia and Trinema, Gromia, &c. ; and though evi- 
dently the fresh waters are by no means so rich in types or in 
individual forms as the sea, still my look-out for novelties 
was uot altogether unrewarded. 
The state of knowledge of the structural and develop- 
mental affinities of the known types is as yet so imperfect 
that existent arrangements of this group to be found in books 
are still unsatisfactory. This circumstance renders it a 
matter of difficulty in bringing forward the following new or 
little-known forms, to determine exactly with which to 
begin, although these, indeed, may hardly exceed a dozen. 
Still they demand several new genera for their reception. 
The comparative fewness of generic types in the fresh waters 
renders the intervals between them seemingly wider than 
if the species were as numerous as those of certain marine 
groups. The sequence in which I shall put them before 
those who take an interest in such forms is, therefore, a 
matter of the less importance. I shall then commence with 
two forms which come the closest to the marine ‘ Radiolaria’ 
of Haeckel, by reason of possessing solid parts or skeleton 1 
(for none of them actually belong to that extensive group, so 
lavishly rich in marvellously beautiful forms, by reason of 
the absence of the seemingly all-important part of the organi- 
zation — the ‘ central capsule’), and then I shall pass on to 
other * shell-less ’ forms more approximating to the ordinary 
Actinophrys, leaving for the latter part of this communication 
the consideration of another series showing affinities rather 
in the direction of the Gromidse and of the Difflugise. I 
shall first venture to offer some remarks on the forms as they 
thus present themselves, and defer special generic and 
specific descriptions to the end of my communication. 
1 Haeckel, ‘Die Radiolarien (Rhizopoda radiaria)’, pp. 25, 69, 243. 
VOL. IX. — NEW SER. 
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