Food taken in at one or more definite mouth-spots, or by a true mouth,
or by absorption; or nutrition holophytic.
Order 1.--PROTOMASTIGACEAE. Contractile vacuole simple, one or more,
or absent; either holozoic, ingesting food by a mouth-spot (or 2 or
more), saprophytic, or parasitic.
Family 1.--OICOMONADIDAE. Flagellum 1, sometimes with a tail-like
posterior prominence passing into a temporary flagellum, but without
other cytoplasmic processes. _Oicomonas_ (Kent); _Cercomonas_
(Dujardin) (Fig. 1, 32, 33); _Codonoeca_ (James-Clark), with a
gelatinous theca.
Family 2.--BICOECIDAE. Differs from _Oicomonadidae_ in a unilateral
proboscidiform process next the flagellum; often thecate and
stalked, forming branched colonies, like Choanoflagellates in habit.
_Bicoeca_ (J.-Cl.), _Poteriodendron_.
Family 3.--CHOANOFLAGELLIDAE (Choanoflagellata, Kent;
Craspedomonadina, Stein). As in previous families, but with
flagellum surrounded by an obconical or cylindrical rim of
cytoplasm, at the base of which is the ingestive area. The cells of
this group have the morphology of the flagellate cells (choanocytes)
of sponges. They are often colonial, and in the gelatinous colony of
_Proterospongia_, the more internal cells (Fig. 2, 15) pass into a
definite "reproductive state." Many stalked forms are epizoic on
Entomostracan Crustacea.
(a) Naked forms often stalked: _Monosiga_ (Kent), stalked
solitary; _Codosiga_ (Kent) (Fig. 2, 3), stalked social;
_Desmarella_ (Kent), unstalked, and _Astrosiga_ (Kent), stalked,
form floating colonies.
(b) Forms enclosed in a vase-like shell: _Salpingoeca_ (J.-Cl.);
(Fig. 2, 1, 6, 7) recalling the habit of _Monosiga_ and _Cod
siga_; _Polyoeca_ forming a branched free swimming colony.
(c) Forms surrounded by a gelatinous sheath: _Proterospongia_
(Kent) (Fig. 2, 15); _Phalansterium_ (Cienk.) (Fig. 1, 12), has a
slender cylindrical collar, and a branching tubular stalk.
Family 4.--HAEMOFLAGELLIDAE. Forms with a complex nuclear apparatus,
and a muscular undulating membrane with which one or two flagella
are connected, parasitic in Metazoa (often in the blood).
_Trypanosoma_ (Gruby) (Fig. 1, 21, 22), _Herpetomonas_(Kent),
_Treponema_ (Vuillemin)(= _Spirochaete_, auctt., nec. Ehrbg.).
Family 5.--AMPHIMONADIDAE. Flagella 2 anterior, both directed
forward, equal and similar; in stalk sheath, &c., often recalling
Choanoflagellata, _Amphimonas_ (Kent), _Diplomitus_ (Kent);
_Spongomonas_ (St.), with thick branching gelatinous sheath.
Family 6.--MONADIDAE. Flagella 2 (3), anterior all directed
forwards, one long the other (or 2) accessory, short.
_Monas_ (St.); _Anthophysa_ (Bory) (Fig. 2, 12, 13), with the stalk
composed of the accumulation of faeces at the hinder end of the
cells of the colony.
Family 7.--BODONIDAE. Flagella 2 (or 3) 1 anterior, the other (1 or
2) antero-lateral and trailing or becoming fixed at the end to form
a temporary anchor.
_Bodo_ (Ehrb.) (figs. 1, 23-26 and 2, 10). _B. lens_ is the "hooked"
and _B. saltans_ the "springing monad" of Dallinger and Drysdale;
_Dallingeria_ (Kent) with a pair of antero-lateral flagella; _Costia
necatrix_ (Leclerq) is also 3-flagellate; causes destructive
epidemics in fish-hatcheries.
[Illustration: FIG. 2.--Flagellata.
1. _Salpingoeca fusiformis_, S. Kent (Choanoflagellata). The
protoplasmic body is drawn together within the goblet-shaped shell,
and divided into numerous spores.
2. Escape of the spores of the same as monoflagellate and
swarm-spores.
3. _Codosiga umbellata_, Tatem (Choanoflagellata); adult colony formed
by dichotomous growth.
4. A single zooid of the same.
a = nucleus.
b = contractile vacuole.
c = the characteristic "collar" of naked streaming protoplasm.