The _stomach_ may be nearly spherical, ovoid, or elongated and cylindrical. Its walls are formed of large cells, often granular and sometimes brownish, whence a hepatic function has been assigned to them. Its apertures are both surrounded by constricting muscular fibres. The _intestine_ may be simple or divided by a similar constriction into _intestine_ proper and _rectum_. The whole of the alimentary tract, with the exception of the mastax, is richly ciliated within. The rectum opens into the slender non-ciliated cloaca. The intestine is sharply bent upwards and towards the back in the tubicolous forms, but is nearly straight elsewhere; in _Trochosphaera_ and _Apsilus_ it is bent ventrally. In Asplanchnaceae and in _Paraseison_ there is no rectum, the stomach being a blind sac. The so-called _salivary glands_, usually two in number, open into the pharynx or mastax; and the paired _gastric glands_ (Fig. 106, _gg_) open into the oesophagus or stomach. While the prehension of food is usually accomplished by the ciliary current of the disc and pharynx, we have seen that a more active swallowing action takes place in Flosculariaceae and Asplanchnidae, which devour whole Algae, Infusoria, and even other Rotifers, the long spines of _Triarthra_ not availing as a protection. Many Ploima put out the tips of their trophi to nibble at débris, or, in the case of _Diglena_ and _Distemma_, to attack Desmids, or the Infusorian _Stentor_. But this use of the trophi is most efficient in _Ploesoma_. Bilfinger[258] writes: "It has the courage to attack larger Rotifers; thus I was able to observe under the microscope how it fell upon a _Rattulus_ but little smaller than itself and destroyed it. First it plunged the sharp prongs of its mastax deep into the tender frontal area of its unhappy victim; then followed a pumping action of the gizzard, and stroke by stroke the whole contents of the victim's body passed into the brigand's stomach." From this it is an easy transition to the ectoparasitism of _Drilophagus_, _Balatro_, and {213}some species of _Albertia_, which cling to their host by the exserted trophi.