46 Infusoria : What are they !
and handsomest representatives of the Infusorial class as
exemplified by the Stentors or "Trumpet Animalcules," and
the genera Bursaria and Spirostomum. In the third order,
that of the Peritricha, the cuticular ciliary series is entirely
suppressed, a spiral or circular series surrounding the
anterior border, while a second supplementary girdle is
occasionally developed towards the central or posterior region.
This division is interesting as containing the exceedingly
elegant "Bell Animalcules" or Vorticellidae, all characterised
by their normally sedentary habits, and being, as in Vorticella
proper, attached singly to their fulcra of support through
the medium of a complex retractile pedicle, or, as in the case
of Carchesium and Epistylis, building up through repeated
subdivision extensive tree-like colonies. Other Vorticellids,
such as Cothurnia and Vaginicola, inhabit elegant stalked or
sessile protective sheaths or lories, whose orifices are some-
times guarded by opercula or lid-like structures. Some
one or more members of this very characteristic group reward
a dipping from any weed-grown pond. The fourth and last
group of the Ciliata is known as the Hypotricha ; it includes
all infusorial forms which, like Euplotes, Stylonychia, and
Oxytricha, have locomotive cilia developed only on the lower
or ventral surface of the body. These cilia are usually
diversely modified in the same individual, taking the form of
sets, styles, or uncini, and constitute veritable ambulatory
organs wherewith their possessors literally walk, insect-wise,
over the surface of submerged objects.
The animalcules comprised in the relatively small group of
the Tentaculifera—including Acineta, Podophrya, and their
allies—were for a long while regarded as embryonic con-
ditions only of certain Ciliata. The tables have now, how-
ever, been so far turned that not only are they recognised as
constituting an independent series, but they are also shown
to originate from ciliated germs, and consequently represent
an even more highly developed class than that of the Ciliata.
All the Tentaculifera are distinguished by their possession of
tubular, and mostly retractile, tentacle-like appendages, which
are utilised by the free forms for locomotive purposes, but