A BRACKISH WATER COMMUNITY NEAR SOUTHEND. 105
from the land. Salts and water are lost by drainage on to Haven-
gore Island and after heavy rain into Havengore. Evaporation
is compensated by rainfall both directly into the creek and as
drainage from New England Island.
The bottom of the creek is covered by a thick growth of
Ruppia maritima, individual plants being spaced at about the
same density as cultivated corn. The stalks of this plant may
reach six feet in length. Beneath the surface are also vast
masses of Chaetomorpha linum which are entangled with the
Ruppia, so that a dense mat, 3 or 4 feet thick, covers the
greater part of the floor. The Ruppia flowers in late June and
July, and persists throughout the year; the Chaetomorpha, on
the other hand, appears to die out in the winter months. In
December, 1934, and January, 1935, there was an outbreak of
Prorocentrum micans which was the only phytoplankton col-
lected in 1934-5.
The fauna was collected by hand, by tow-netting, by trawling
and by keeping cultures of mud, water and weed in the depart-
mental aquarium : the following animals were found, but this
list is not believed to be complete because of the technical
difficulties involved in collecting among the Ruppia roots and
Chaetomorpha.
Protozoa: Condylostoma magnum, Anomia sp.
Coelenterata: Coryne loveni, Obelia flabellata, Gonothyrea
loveni, Rathkea octopunctata, Diadumene
luciae, D. cincta.
Nemertinea: Lineus gesserensis.
Annelida: Harmothoe spinifera, Nereis diversicolor,
Polydora ciliata, Arenicola marina.
Crustacea: Eurytemora velox, Acartia bifilosa, Idya
furcata, Mesochra lilljeborgi, Cyclopina nor-
vegica, Sphaeroma rugicauda, Idothea n. sp.,
Jaera marina, Ligia oceanica, Gammarus
n. sp. ? duebeni, Corophium volutator,
Praunus flexuosus, Palaemonetes varians.
Insecta : Hydroporus planus, Philhydrus bicolor,
Sigara selecta, Aedes detritus, Tabanid,
Nemotehes sp.