THE NANNOPLANKTON OF BOMB-CRATER POOLS. 237
condition. The forms noted in the' bomb-crater pools were :—
Cylindrotheca gracilis (5), Cymbella sp. (1), Navicula spp. (9),
Nitzschia spp. (7), Nitzschiella acicularis (3), Pinnularia micro-
stauron (1), Surirella ? ovata var. (1), S. sp. (2), Synedra sp. (1).
Cryptophyceae.
This small but very distinct class of the Algae consists almost
entirely of planktonic forms, some of which are so small that
they come easily within the nannoplankton limits. The bomb-
crater pools yielded the following :—Chilomonas ? oblonga (1),
C. paramaecium (2), C. sp. (4), Chroomonas nordstedti (4) (Fig. 8),
Cryptomonas erosa (11), C. ovata (6), C. sp. (4).
DINOPHYCEAE.
Most of the members of this class are free-swimming planktonic
forms and the smaller species are fairly common in the nanno-
plankton. The following forms were noted from the bomb-
crater pools :—Amphidinium ? larvale (2), (Fig. 2), Glenodiniwn
? cinctum (1), G. ? edax (2), G. spp. (7), Gymnodinium spp. (4),
Peridinium ? anglicum (1), P. umbonatum (2), Spirodinium
hyalinum (1).
EUGLENINEAE.
This large and diversified algal class is to be found most
abundantly in water rich in dissolved organic material. In the
bomb-crater pools they were found more frequently and of
more varied character than those of any of the other groups.
The list of forms noted is as follows :—Anisonema acinus (1),
Astasia sp. (1), Cryptoglena pigra (1), Euglena acus (2), E genicu-
lata (1), E. intermedia (1), E. ? limnophila (1), E. mutabilis (2), E.
pisciformis (4), E. Spirogyra (4) E. tripteris (9), E. spp. (16),
Lepocinclis acicularis (1), L. ovum (6), L. teres (1). L. texta (8),
Menoidium sp. (1), Phacus longicauda (1), P. oscillans (2), P.
Pleuronectes (4), P. pyrum (3), P. triqueter (6), Trachelomonas
acuminata (2), T. caudata (3), T. euchlora (1), T. 1 fluviatilis (1),
T. hispida and vars. (8), T. ? intermedia (1), T. ? oblonga (1), T.
perforata (2), T. rugulosa (1), T. volvocina (13).
MYXOPHYCEAE.
Blue-green algae are not very common in the nanoplankton
the chief representatives being small accidental pieces of such
filamentous forms as Oscillatoria, &c. There are no forms
free-swimming by means of flagella or cilia. The only records
from the bomb-crater pools were :—Anabaena ? affinis (1),
Merismopedia sp. (1), Oscillatoria spp. (3), Pseudanabaena
catenata (3).