[Illustration: FIG. 107.—Male Rotifers. (After Hudson.[252]) 1, _Floscularia campanulata_; 2, _Lacinularia socialis_; 3, _Notops brachionus_; 4, _Synchaeta tremula_; 5, _Asplanchna ebbesbornii_; 6, _Brachionus urceolaris_; 7, _Salpina mucronata_; 8, _Pedalion mirum_.] EXTERNAL FEATURES.[253]—The body is divided into three regions: (1) the _head_, ending in the _disc_, which bears the ciliary _wreath_; (2) the _trunk_, containing the viscera; (3) the _foot_, which only contains muscles, nerves, and cement-glands. The general form of the BODY varies greatly: it is spherical in _Trochosphaera_, ovoid in Asplanchnidae, conical in Scirtopoda, Triarthridae, and _Synchaeta_; moderately elongated in the majority of the Ploima, among which some forms are very flat, like _Pterodina_, _Metopidia_, and _Brachionus_; shortly elongated and cylindrical in _Hydatina_ (Fig. 106), Notommatidae, and many others. In _Taphrocampa_ it is cylindrical and segmented, while the segments are {201}telescopic in the Bdelloida, both ends being retractile into the middle segment. In most attached, tube-dwelling forms the body is ovate, tapering behind into the elongated stalk-like foot. The FOOT at the hinder end of the body is usually more or less jointed; in _Pterodina_ and _Brachionus_ it is long, transversely wrinkled, and retractile. Usually it terminates in a couple of acute, mobile toes, perforated at the tips by the ducts of the pedal glands (Fig. 106, _fg_), whose viscid secretion serves to anchor the animal. In _Rotifer_ there are three of these toes, which are retractile, and in addition there are in this genus, as in most of the Bdelloida, toe-like pointed spurs in pairs on the more proximal joints of the foot. In _Callidina_ the spurs are often perforated, and the toes are replaced by numerous openings on the last joint of the foot (Fig. 109, A); while in _Discopus_ the end of the foot expands into a large disc, with numerous pores for the exudation of the pedal cement, and there are no spurs. In _Pedalion mirum_ the foot is represented by two tubular processes ciliated at the apex and at the outer side near the base (Fig. 117, _f_). These are inconstant in size and form, that of one side being sometimes reduced or absent, while both are absent in the closely allied species _P. fennicum_. In Melicertidae and Flosculariidae the long foot ends in an expanded disc, which is cupped and ciliated in the larva (Fig. 112, B) and in the larva-like male (Fig. 107); but in two species it is prolonged into a long flexible thread which is not contractile. The foot is also elongated in the Bdelloid genus _Actinurus_ and the Ploimal genus _Scaridium_. It forms a mere ventral disc in _Apsilus_ (and _Atrochus?_), and is absent in Asplanchnidae (except _Asplanchnopus_), Triarthridae, and Anuraeidae, and in the genera _Trochosphaera_ (Melicertaceae) and _Pompholyx_ (Pterodinidae).