238
THE ESSEX NATURALIST.
ZOOFLAGELLATA.
Colourless flagellates of many different kinds occur in the
nannoplankton, but they are usually very delicate and may
quickly disappear. They are also, as a rule, more difficult to
identify than the pigmented flagellates. The following are the
records from the bomb-crater pools :—Anthophysa vegetans,
detached colonies (2), Bicoeca planktonica3 (1), (Fig. 4), B.
socialis (1), Bodo ? fusiformis (1), B. ? lens (2), B. spp. (7), Cerco-
bodo spp. (5), Cladomonas ? fruticulosa (2), Collodictyon sp. (3),
Desmarella moniliformis (1), Monas sp. (2), Monosiga ovata (1),
Oicomonas mutabilis (1), O. ocellata (8), Physomonas vestita (2),
Rhynchomonas nasuta (5), Stokesiella sp. (1), ? Trepomonas sp.
(1).
Rhizopoda.
It is somewhat surprising that this group should be represented
at all in the nannoplankton, but actually it is no unusual thing to
find small Amoebae in samples of centrifuged water. It
may be that these have been adhering to small particles of
detritus floating about in the water and this may also account
for the other forms seen. The forms noted were :—Amoeba
guttula (3), A. Umax, type and small varieties (3), A. radiata (1),
A. striata (1), A. spp. (7), ? Biomyxa sp. (1), Diplophrys archeri (3),
Trinema enchelys (1).
Heliozoa.
Only occasionally are representatives of this group found in the
nannoplankton. They are, of course, very small forms and
possibly some have not yet been described. The bomb-crater
pools yielded the following :—Acanthocystis erinaceus,
apparently typical, but only 8u (1), A. ? pertyana (1), and two
or three others from four pools which could not be definitely
placed.
Ciliata.
Ciliates as a rule are too large to be included in the nanno-
plankton, but there are a few which are on the border line and
which occur fairly frequently among the smaller organisms. From
the bomb-crater pools were noted :—Chilodon cucullulus (1),
Coleps hirtus (3), Cyclidium glaucoma (2), Didinium sp. (1) and
a few others from several pools not determined.
To the foregoing enumeration of the various forms that have
been recorded a word or two may be added about their occur-
rence in the different pools. The number of species found
3 See note at end.