102 EPPING FOREST
which are not absent from the Forest. These include
the Bell Animalcules or Vorticellae, attached by long
retractile threads to shells and other objects, constantly
jerking up and down. Species with branched peduncles,
known as Epistylis, are represented by some four or five
species. Then again there are the Stentors, which are
the largest of the Infusoria, of a funnel shape, with a
fringe of delicate hairs around the mouth, for ever in
motion. There is Stentor polymorphus in the southern
ponds, with Stentor mulleri, and sometimes Stentor
niger. To these may be added, as of universal inter-
est, such things as Vaginicola crystallina, and the free-
swimming Stylonichia lanceolata, and pustulata, as well
as Paramecium aurelia, Trachelius ovum, and Bursaria
truncatella. Different forms of Euglena are always to
be found in immense numbers, so that not only Euglena
viridis, but also Euglena acus and Euglena longicauda,
as well as Euglena deses, may be obtained from nearly
all parts of the Forest.
Hydrozoa. Of all the animals which inhabit ponds and
ditches there are none to surpass the Fresh-water Hydra
in interest, not only as representing the oceanic Hydrozoa,
but from its remarkable history and possibilities. The
green Hydra is the most common, and has been obtained
in the southern part of the Forest, attached to aquatic
plants. It has the advantage of being so large that it
may be watched with the naked eye, expanding and
withdrawing its arms, or tentacles, and catching its
prey. There are also a brown and an orange-brown
species, sometimes found mixed with the green species.
No reference need be made here to the remarkable
powers possessed by this little animal—of its being able
to turn itself inside out, to produce little hydras by
buds from its own body, and to suffer splitting into two
halves, so that each half will heal up again and become
a separate individual. All of this is now a matter of
history, and has made the Hydra a classical object to the
naturalist.
Polyzoa. No objects are more earnestly sought by the pond-
hunter than the Fresh-water Polyzoa, of which two
species at least occur in the Forest district. These
are, Fredericella sultana, obtained near Chingford and
Snaresbrook ; and the other is Lophopus crystallinus from
Chingford. Undoubtedly they are somewhat rare, and
must be carefully hunted for, but, when found, will
amply repay all the trouble. They attach themselves
to aquatic plants, such as duckweed, in such manner as
to be turned away from the light. When at rest, these
Polyzoons expand their tentacles and present a most
attractive appearance, but when these are withdrawn,
they only resemble a lump of jelly.
Rotifera. The Rotifers, or wheel-bearers, are, as a whole,
the most attractive of pond animals, inasmuch as some
of them may always be found, and they present a very
great variety of forms. Some of them are fixed, but the
greater portion are free swimmers. Possibly there are
more than three hundred known British species ; at any