MARINE NATURAL HISTORY OF THE COLNE ESTUARY. 167
In the Pyefleet the interesting tube building Worm, Sabella,
used to be very abundant, but is much less so now, and many
Ascidians can be collected on the shores, chiefly belonging to the
genera Ascidia and Cioni. The most usual compound Ascidian is
Botryllus. Sometimes a few kinds of Actiniae may be seen
attached to the stick-beacons. Along the shore of the Colne at
low water, on the east side above Brightlingsea Creek, there is
in some years an extensive growth of large Algae, and amongst
them a number of interesting things may be collected. Very
fine Sabella are common, and large Terebellae can be procured.
For many purposes the entrance to Blakestone Hole is an ex-
cellent collecting ground. When the tide is low several Compound
Ascidians and more than a dozen species of large marine Alga can
be obtained from the shallow water running out, and entangled
amongst them may be found many specimens of Pygnogonum,
and a number of small crustaceans. From the sand-
banks may be dug out several species of worms, amongst the
chief of which are Terebella, Nephthys and Nereis. Somewhat
higher up, Arenicola abounds, and the Mollusc Pholas dactylus
occurs, boring into the black clay. I think I once found the
worm Cirratulus borealis in the clay of the bed of the stream.
From the mud in St. Osyth Creek several kinds of worms
may be be obtained, amongst which Nephthys and Nereis are the
most common, some of the latter being of an unusually green
colour. The most common molluscs are Scrobicularia piperata and
Tellina solidula.
I feel sure that this is a very imperfect list and that many
other things must occur.
My dredging and trawling operations off Mersea have been
mainly confined to the sea which lies towards the west, outside the
2nd and 4th Floating Beacons, since, in that part there is a fairly
clean bottom. Nearer Mersea we usually come to mud, and further
out than the 4th Beacon there is much sand. One of my chief
objects in dredging has been to collect sundry species of Algae
attached to small stones, which will live fairly well in my aquaria.
A number of interesting species can be obtained, but on the
whole this district is strikingly inferior to the coast of Devon-
shire and even to the Orwell and Stour rivers.
I do not think some animals can be so common as they used
to be, such as the small worm Lepidonotus squamatus and a small
purple. Nudibranch, of the genus Eolis. Doris, however, is still
met with, and the small worm Polynoe.