Page:EB1911 - Volume 10.djvu/483



 known generally as “plastids” or “chromatophores” impregnated with a lipochrome pigment, whether green (chlorophyll), yellow or brown (diatomin or some allied pigment), or again red (chlorophyll with phycoerythrin). In the active condition of such coloured holophytic forms there is usually at least one anterior “eye-spot,” of a refractive globule embedded behind in a collection of red pigment granules. The single anterior “flagellum tractellum” of so many of the larger forms acts by the bending over of its free end in consecutive meridians, so as to describe a hollow cone with its apex backwards: we may imitate this by bending the head of a slender sapling round and round while it is implanted in the soil; and the result is to push the water backwards, or in other words to pull the body forwards, the whole rotating on its longitudinal axis as it moves on (Y. Delage). An anterior lateral trailing flagellum may modify this axial rotation, and help in steering. When the animal is at rest—attached by its base or with its body so curved as to resist onward motion—the current produced by the tractellum will bring suspended particles up against the protoplasm at its base of insertion. As noted by E. R. Lankester, the posterior flagellum of many Haemoflagellates, like that of the spermatozoon of Metazoa, propels the cell by a sculling motion behind; he terms it a “pulsellum.” Such flagellar motion is distinct from that of cilia, which always move backwards and forwards, with a swift downstroke and a slower recovery in the same plane; though where the flagella are numerous they may behave in this way, and indeed flagella agree with cilia in being mere vibratory extensions of cytoplasm. Symmetrically placed flagella may have a symmetrical reciprocating motion like that of cilia.

Many of the Flagellata are parasitic (some haematozoic); the majority live in the midst of putrefying organic matter in sea and fresh waters, but are not known to be active as agents of putrefaction. Dallinger and Drysdale have shown that the spores of Bodo and others will survive an exposure to a higher temperature than do any known Schizomycetes (Bacteria), viz. 250° to 300° Fahr., for ten minutes, although the adults are killed at 180°.

The Flagellata are for the most part very minute; the Protomastigopoda rarely exceeding 20 in length. The Euglenaceae contain the largest species, up to 130 in length, exclusive of the flagellum.  Our classification is modified from those of Senn (in Engler and Prantl, Pflanzenfamilien) and Hartog (in Cambridge Natural History).

Food taken in by pseudopodia at any part of the body.

Order 1.—HOLOMASTIGACEAE. Body homaxial with uniform flagella. Multicilia (Cienkowski); Grassia (Fisch, in frog’s blood and gastric mucus).

Order 2.—RHIZOMASTIGACEAE. Flagellum 1, 2 or few, diverging from anterior end. Mastigamoeba (F.E. Schulze).

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.—. 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.—. 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.— (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.—. 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.—. Flagella 2 anterior, both directed forward, equal and similar; in stalk sheath, &amp;c., often recalling Choanoflagellata, Amphimonas (Kent), Diplomitus (Kent); Spongomonas (St.), with thick branching gelatinous sheath.

Family 6.—. 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.—. 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