THE ENTOMOSTRACA OF EPPING FOREST. 205
kinds of tape-worms (62), larvae of Trematodes, and a fair
number of Nematodes. Among the latter are Cucullanus elegans,
which is known to live at first encysted in Cyclops, and then to be
directly transferred to the Perch, in which it matures, and
Dracunculus (Filaria) medinensis which, in tropical countries, is
also found in the larval state in Cyclops, and in the adult state in
man, although the exact mode of its transference has not been
made out.
Of diseases, as distinguished from endo-parasitism of the
kind just alluded to, numerous cases have been reported, but
they mostly belong to one or other of two main types. In the
first a comparatively large fungus of the Saprolegnia group gains
access to the body-cavity and spreads its colourless filaments in
all directions, eventually filling up nearly every available crevice.
The other type of disease is produced by the enormous multipli-
cation in the blood of extremely minute granules of various
shapes, most of which are known by the rather vague term of
Microsporidia. These are sometimes coloured, and it is no
uncommon thing to take specimens, especially of Simocephalus
velutus and Chydorus sphaericus which are quite red from this cause.
Methods of Collecting, Examining, and Preserving.
The methods used for collecting the majority of the Ento-
mostraca do not differ essentially from those employed for other
forms of pond-life. A wide-mouthed bottle tied to a walking
stick, dipped into the water in an inverted position, and then
suddenly turned over, will secure a limited number of specimens
from almost every desired position. A much better piece of
apparatus is, however, a small conical net (say 6" diameter) to
the bottom of which a glass collecting tube or small bottle has
been affixed. The net may be made of almost any fine-meshed
materia], but the best and most durable is undoubtedly the
silk gauze prepared for sifting flour and known as centrifugal or
millers' silk gauze. This is made in various degrees of fineness,
but I find that, for Entomostraca, No. 9, with about 100 threads
to the inch, is quite fine enough. Such a net, attached to a
stick, can be swept through the clear water, worked about
amongst weeds, or dragged over the bottom as desired, and the
captured animals, washed down into the glass tube, can then be
roughly examined with the naked eye or a pocket lens.
In addition to the above, it is often desirable to have a net
attached to a line so that it can be thrown out as far as possible.