A DAY ON THE CROUCH RIVER. 149
and other seaweeds. Specific determination in this puzzling genus
was not attempted. One of the hard Escharae was noticed, and some
fine pieces of "Lemon-weed" or "Sea-mat" (Flustra foliacea and
the more delicate F. papyracea), were brought up. These animal
colonies being flat and frond-like, are invariably taken for sea-weeds
by the oι πολλόι, but the use of a lens soon dispels this idea and
shows the numerous closely-clustered cells, each inhabited by its own
Polypide. Gosse calculated that in F. foliacea there were 13,440 cells
to the square inch. For figure, see his "Tenby," pl. x. Although
here called "Lemon-weed," the scent is little like that of a lemon,
but more resembles verbena or pine-apple. Alcyonidium gelatinosum,
somewhat resembling sticks of barley-sugar, occurred, but in nothing
like the abundance we found it in the Orwell (E. N. iv. 170).
Membranipora pilosa was common, matting together several Sea-
weeds (Algae) and Sertularians.
The somewhat repulsive looking Ascidians or sea-squirts, whose
local name need not be given, were in the greatest abundance. They
bear considerable resemblance to oriental and ancient wine-skins,
whence their scientific name. They were mostly the common
Ascidia virginea and were of all sizes and forms consistent with the
species, and were attached to everything in the shape of a stone or
shell, often in bunches. Molgula oculata was found sparingly
towards the mouth of the river opposite Hollywell, looking like little
bullets of sand; they were quite indistinguishable until they were
touched. The currant-squirter, Cynthia (Styela) grossularia, looking
like a small pink or brick-red sea-anemone when closed, was
particularly abundant on the shells of the oyster. It is locally
termed "pock" ; when squeezed these smell much like cucumber.
The life-history of these Ascidians or Tunicata affords an excellent
example of ancestral degeneration ; they all have a free-swimming
fish-like larva.
Now coining to the Mollusca. We found Pholas candida1 alive,
boring into chalk nodules that were dredged up. These had
probably been used originally to face the sea-walls, some of the
lumps had been completely riddled by this animal. The soft,
wet chalk was easily split or cut through with the cull-tack and so
the thin and extremely brittle shell could be easily obtained
perfect ; many living specimens were found. One or two dead and
1 When at Burnham on 14th February last, Mr. Crouch got a fine living specimen of Pholas
crispata. Shell 3 inches long by 13/4 inches broad. The animal with syphons measured almost
exactly six inches.