260
THE ESSEX NATURALIST
and a temperature range of 5.5°-6.l° C, Although the salinity
from January 1934 to March 1935 was variable, increasing to its
highest level of 27.9‰ in October 1934, over a period of 25
years a considerable drop in salinity was to be expected, the
probable effects of which were discussed by Howes (1939: 383-4).
On 17th March 1959, after a winter of heavy rains, the salinity
recorded was 13.71‰ (temperature 7.5° C), but the dry summer
of 1959 reduced the water content of the Creek so that on 15th
March 1960 the salinity was again high; 27.32‰ (temperature
10.9° C). It would appear that the salinity of the Creek has not
become progressively lower, but varies considerably from year to
year.
In 1959 specimens of E. crustulenta were also found on Ruppia
in a drainage ditch to the south of the Creek, and opposite
Creeksea on the south bank of the River Crouch, where they
were growing on barnacle shells and under large stones at the
Scale equals 100μ.
Figure 1. Electra crustulenta (Pallas), intertentacular organ of pre-
served narcotized specimen, viewed from the proximal side of
the operculum, (op.).
All scales equal 100μ.