48 Infusoria: What are they ?
the entire absence of such a faculty or structure among the
plants, has rendered practicable the isolation of a very exten-
sive series of animal forms, whose members, it is anticipated,
may be almost indefinitely augmented. Even as so far
known, the number of flagellate Infusoria is as considerable
as that of the Ciliata, and promises in the long run to be
transformed into a very substantial majority. A long and
intimate acquaintance with the flagellate class has enabled
me to propose its subdivision into three primary series, which
may take rank with the several orders of the Ciliata already
enumerated. The characters presented by these Flagellata
are indeed far more substantial in kind than those cited in
connection with the Ciliata. They relate not merely to the
nature and distribution of the locomotive appendages, but to
important distinctions in the characters of the ingestive
system. Thus in one very extensive series, for which I have
proposed the title of the Flagellata-Pantostomata, there is
no distinct mouth or oral aperture, food-substances being
received indifferently—after the manner of an Amaeba—at
all points of the cuticular surface. Such genera as Monas,
Heteromita, or Anthophysa afford fitting examples of this
Pantostomatous group. In a more advanced section or order
the area of food-ingestion, while not distributed over the
entire surface, nor so limited as to form a distinct mouth,
occupies a discoidal interspace of considerable extent at the
anterior extremity of the body. It is this order, distinguished
by me by the title of the Choano-Flagellata, or "Collared
Monads," that embodies those very minute and beautiful
forms in which an extremely delicate extensile and contractile
collar-like expansion embraces the base of the flagellum, and,
through the adhesiveness and circulation of its substance,
constitutes a marvellously elaborate and efficient trap for the
capture of passing food. For the first discovery of this very
remarkable flagellate group Science is indebted to Professor
H. James-Clark of America, who, in the year 1866, figured
and described no more than four distinct species. A few
years later these several types were discovered by myself
upon this side of the Atlantic, and, through the devotion of