200 THE ENTOMOSTRACA OF EPPING FOREST.
conveniently called "ephippial females." So far as can be
judged by their appearance, the Ostracoda and Copepoda only
produce eggs of a single type. In these cases the eggs seem to be
intended for immediate development, but there can be no doubt
that many also possess some power of remaining dormant.
Much more light is wanted, however, on this subject.
Yet another point may be briefly referred to, as it is a very
important one to the collector. The eggs of the animals belong-
ing to the different sub-divisions of the Entomostraca hatch out
in very different ways. Thus the egg of a Copepod develops
into a typical "nauplius," i.e., a little free-swimming unsegmented
ovoid larva with only three pairs of appendages. After several
preliminary moults, at each of which new appendages make their
appearance, the larva suddenly (at a moult of course) takes on
the typical Copepod form. By a number of further moults, each
accompanied by the development of new appendages (except in
the parasitic forms, where various retrogressive changes take
place), the adult stage is finally reached. The Phyllopoda also
hatch as nauplii, but these possess behind the three main pairs
of appendages a series of little paired lobes, foreshadowing the
future foliaceous feet. The Ostracoda are provided at birth
with a bivalve shell in the same way as the adults, but the little
animal within is in other respects a nauplius. The Branchiura
hatch out in a more advanced stage than either of the foregoing
groups, but the young is still a larva differing from the adult in
many important particulars, but especially by the absence of the
large suckers. In the remaining group, the Cladocera, the
young, with only one exception, leave the egg in all essential
particulars similar to the adult. They require, however, to moult
many times before assuming the characteristic outlines of the
species. The exception referred to is in the case of the young
hatched from the resting-eggs, and from these only, of Leptodon
hyalina. These are in the form of a Phyllopod nauplius. From
the foregoing facts it will be seen that the task of determining
all the forms of Entomostraca that one finds is not altogether an
easy matter. The only safe rule for beginners is never to
attempt to name a form that does not show very good evidence
of being adult.
Food.
Considered as a whole the Entomostraca appear to be
decidedly carnivorous in their tastes. But, except among the