{160}[Illustration: FIG. 61.—Various forms of Suctoria. 1, _a_ and _b_, two species of _Podophrya_; _c_, a tentacle much enlarged; 2, _a_, _Acineta jolyi_; 2, _b_, _A. tuberosa_, with four ciliated buds; in 6 the animal has captured several small Ciliata; 8, _a_, a specimen multiplying by budding; 8, _b_, a free ciliated bud; 9, _a_, the entire colony; 9, _b_, a portion of the stem; 9, _c_, a liberated bud. _a_, Organism captured as food; _b.c_, brood-cavity; _bd_, bud; _c.vac_, contractile vacuole; _l_, test; _mg.nu_, meganucleus; _mi.nu_, micronucleus; _nu_, nucleus; _t_, tentacle. (From Parker and Haswell, after Bütschli and Saville Kent.)] {161}The mechanism of suction is doubtful; but from the way particles from a little distance flow into the open funnels of _Choanophrya_, it may be the result of an increase of osmotic pressure. The external pellicle of the tentacles is marked by a spiral constriction,[180] which may be prolonged over the part included in the sheath. The endosarc is rich in oil-drops, often coloured, and in proteid granules which sometimes absorb stains so readily as to have been named "tinctin bodies." It usually contains at least one contractile vacuole. In _Dendrocometes_ (and perhaps others) the whole cell may become ciliated, detach itself and swim off; this it does when its host (_Gammarus_) moults its cuticle. In fission or budding we have to distinguish many modes. (1) In the simplest, after the nuclear apparatus has divided, the cell divides transversely; the distal half acquires cilia and swims off to attach itself elsewhere, while the proximal remains attached. The tentacles have previously disappeared and have to be formed afresh in both. (2) More commonly fission passes into budding on the distal face; a sort of groove deepens around a central prominence which becomes the ciliated larva (Fig. 62, _em_); the tentacles of the "parent" are retained. This process passes into (3) "internal budding," where a minute pit leads into a bottle-shaped cavity.[181] (4) Again, the budding may be multiple, the meganucleus protruding a branch for each bud, while the micronucleus, by successive divisions, affords the supply requisite. _Sphaerophrya_ (Fig. 61, 6) and _Endosphaera_ multiply freely by fission within their Ciliate hosts, and were indeed described by Stein as stages in their life-cycle. Conjugation of the same type as in most Ciliates has been fully worked out in _Dendrocometes_ alone, by Hickson,[182] who has found the meganuclei (though destined to disorganisation) conjugate for a short time by the bridge of communication before the reciprocal conjugation of the micronuclei.