xliv
Journal of Proceedings.
of rivers and ponds that this is so. The plant was first noticed in
England about 1847, and is now a pest in almost every river in the
country ; were sexual reproduction added to its marvellous powers of
increase by the growth of the most minute fragments, all our streams
would soon be choked.
At Chigwell all were safely housed under Mr. and Mrs. Wilson's
hospitable roof, where a hearty welcome was found.
After tea an Ordinary Meeting (the twenty-ninth) of the Club was
held, the President in the chair, who commenced the business by pro-
posing a hearty vote of thanks to their kind host and hostess for the
reception given to the Club that afternoon.
Mr. Henry Walker seconded in a few felicitous words, and the vote was
given by acclamation.
Mr. Wilson in reply said that every member of the Club was most
welcome, and he hoped such meetings would bind them more and more
strongly together as a brotherhood united by common feelings and wishes
to study Nature, and enjoy the charms of the country.
Messrs. Robert H. Eve and J. H. Porter were balloted for, and elected
members of the Club.
Mr. Saville Kent then gave a short address on—
The Study of the Water-Mites or Hydrachnidae.
Some ten or twelve years previously he had devoted a short interval to
the study of this group, and now proposed to take it up again and as far
as possible work out a monograph of the British species. The Hydrach-
nidae constituted a distinct family of the Acarina or Mites, of exclusively
aquatic habits, and specially adapted by the development upon their limbs
of long fine swimming-hairs for leading a natatory existence. The
majority of the members of this group are eminent for their brilliant
colorations—scarlet, crimson, green, yellow, and brown being among the
predominating hues. With but little trouble they may be mounted as
permanent objects for the microscope, and thus constitute in connection
with their bright colours and often grotesque shapes a valuable accession
to the collector's cabinet. By keeping the species isolated in separate
bottles it is easy to arrive at a knowledge of their entire life-history.
Small Entomostraca, such as Daphnias or Ostracoda, should be supplied
every few days as food; the Hydrachnidae, like their congeners the true
Spiders, being eminently predatory, and requiring a constant supply of
living pabulum. A small fragment of water-weed should be likewise
added to each bottle for the little creatures to eat and deposit their ova
upon. These ova, which generally partake of the brilliant colouring of
the adult mites and form exquisite objects for the microscope, especially
when viewed with the aid of the parabolic illuminator, are enclosed
within a transparent, often delicately reticulate film of mucus, and give
birth, usually at the end of a fortnight, to minute hexapod larvae totally
unlike the parents. In some cases these larvae throughout their develop-
ment to the parent form maintain a similar free swimming existence;
but in more exceptional instances they attach themselves as parasites to
various water-insects, and under these conditions undergo their meta-
morphoses, which consist of periodic castings of their skin or ecdysis, by
which process the normal number of appendages, and eventually the cha-
racteristic size, shape, and colour of the adult, is arrived at,