"As the Animal is capable of thrusting these Parts out, or drawing them in, somewhat in the Way that Snails do their Horns, the Figure of them is different in their several Degrees of Extension and Contraction, or according to their Position to the Eye of the Observer, whereby they not only appear in all the various Forms before represented, but seem at certain Times as if the circular Rim of the Wheel or Funnel were of some Thickness, and had two Rows of Cogs or Teeth, one above and the other below that Rim." DIGESTIVE ORGANS.—The _pharynx_ is usually a narrow ciliated tube, which varies in length from genus to genus, but in no other important point, save in Flosculariidae, where it assumes the form of a crop, into which the mouth hangs freely down as a narrow ciliated tube. At its lower end is an enlargement, the _mastax_ or gizzard.[256] This is a strong muscular sac containing the _trophi_ or hard chitinous chewing organs, with an {210}antero-ventral inlet from the pharynx, and a postero-dorsal outlet through which the food passes into the stomach either directly or through a slender gullet (Fig. 106, _oe_). In the ventral wall of the gizzard of most Ploima is a median piece, the _fulcrum_, from which run forwards and upwards two pieces, the _rami_, which are hinged on the fulcrum. The Y-shaped structure formed of these three pieces is called the _incus_ (anvil). At either side of the gizzard and at a higher level is a paired piece, the _malleus_, so called from its resemblance to a hammer, of which the _manubrium_ (handle) looks backwards, and is embedded in the side walls of the mastax, while the toothed claw or _uncus_ looks forwards and inwards, and is hinged at its inner side with the tip of the ramus. As the unci and rami are usually strongly toothed, this gizzard forms a very efficient apparatus for chewing. In some cases, when the pharynx is short and dilatable, the points of the unci and rami may be protruded for biting, for clinging to the host (in the parasitic genera _Albertia_ and _Drilophagus_), or for the prehension of food (Rattulidae, etc.). [Illustration: FIG. 111.—Diagram of trophi. (After Hudson.) A, Malleate; B, submalleate; C, virgate; D, forcipate; E, malleoramate (_Melicerta_); F, incudate (_Asplanchna_); G, uncinate (_Stephanoceros_); H, ramate (_Rotifer_). _f_, Fulcrum; _i_, incus; _ma_, manubrium (malleus in G); _r_, ramus; _un_, uncus.]