NOTES—ORIGINAL AND SELECTED.
181
abundant as to form a positive hindrance to the passage of the
wherries and other vessels. At other seasons of the year, the
"sponge-weed," as it was called locally, could only be obtained
by dredging. A very remarkable thing about the balls of alga
was the wonderful tenacity of life which they possessed. I
have kept a specimen in ajar from Easter, 1899, until towards
the end of last year, i.e. for nearly nine years before it
decayed. During the whole of this time, with the ex-
ception of the last month or so, it maintained a green and
healthy appearance although it did not perceptibly increase in
size. These algal balls were composed of branched threads
radiating from a centre and probably originated by young plants
attaching themselves to small objects capable of being rolled about
by the movements of the water, thus giving the alga a chance to
develop equally in all directions. Dr. Wesenberg-Lund1 has
made some very interesting observations on these balls in one of
the Danish lakes and has shown that they were formed only in
comparatively shallow water on a sandy bottom. With regard
to the floating, there was no doubt that it was directly due to the
formation of bubbles of gas under the influence of sunlight,
but it was rather difficult to understand why this should only
take place in the spring. Dr. Wesenberg-Lund believed that
the explanation was to be found in the decrease in the trans-
parency of the water towards the end of May, due to the great
increase of plankton organisms about that time. So far as I
know Cladophora aegagropila has not been found in Essex in the
form of balls, but it probably occurs in some of its other
forms, such as little cushions attached to submerged objects,
forming a felted mass on the bottom, &c. It has been stated
that in some parts of the country where the balls occur,
the children used them as sponges with which to clean their
slates, a purpose for which they seem well adapted.—
D. J. Scourfield, F.R.M.S., Leytonstone, May 21st, 1908.
GEOLOGY.
A Note on the Stone of the Font at Coggeshall
Church.—The peculiarity of this font, from a non-ecclesiastical
point of view, is the particular stone from which it was
sculptured. I do not think it has any technical name, but it
1 " Sur les Aegaeropila sauteri du lac de Soro."- Oversigt over det Kgl. Danske Videnskabernes
Selskabs, Forhandlinger, 1903. No. 2.