Delage has well explained the action of the single anterior flagellum which waves in a continuous spiral like a loaded string whirled round one's head; it thus induces a movement of the water, beyond its actual range, backwards and outwards, maintained by a constant influx from behind, which carries the cell onward at the same time that it necessarily rotates round its axis. If there is a pair of symmetrically placed flagella they co-operate like the arms of a swimmer; when the second flagellum is unilateral the motion is most erratic, as seen in the Bodonidae (and the zoospores of many Chytridieae, which have most of the characters of the Flagellates, though habitually removed to the Fungi).
The colouring matter is chlorophyll or some allied colouring matter. In the yellow and brown forms the additional pigment is termed loosely "diatomin," but its identity with that of Diatoms is in no case proved.
Notably in the Craspedomonadidae, where transverse division also occurs. See Raoul Francé, Die Craspedomonadineen (Buda-Pesth, 1897).
And also in the "Monads," described by Dallinger and Drysdale, see above.
In Cercomonas dujardinii, Polytoma uvella, and Tetramitus rostratus the gametes resemble the ordinary forms and are isogamous. In Monas dallingeri and Bodo caudatus conjugation takes place between one of the ordinary form and size and another similar but smaller. In Dallingeria drysdali the one has the ordinary size and form, the other is equal in size, but has only one flagellum, not three; in Bodo saltans they are unequal, the larger gamete arising in the ordinary way by longitudinal fission, the smaller by transverse division. Doubt has been thrown on the validity of our authors' results by subsequent observers abroad; but I can find no evidence that these have even attempted to repeat the English observations under the same severely critical conditions, and therefore consider the attacks so far unjustified. Schaudinn has observed conjugation between Trichomonas individuals which have lost their flagella and become amoeboid; also in Lamblia intestinalis and in Trypanosoma (Halteridium?) noctuae (Fig. 39) "Reduction-divisions" (see p. [75], note 1) of the nuclei take place before fusion, and the nuclear phenomena are described as "complicated" (Arb. Kais. Gesundheitsamte, xx. 1904, p. 387). Paramoeba eilhardii in its adult state is colourless, amoeboid, multiciliate. It forms a brood cyst, from which are liberated flagellate zoospores, with a chromatophore, which reproduce by longitudinal fission in this state. They may also conjugate.