ORDER I. FLOSCULARIACEAE.—Females mostly tubicolous, attached by a long contractile foot. Disc produced into a wide funnel-shaped contractile cup, produced into lobes with long setae (_Floscularia_) or coarse cilia (_Stephanoceros_), or entire (Apsilidae); an outer row of fine cilia rarely present; trochus a horseshoe, open behind. Oral funnel a slender tube hanging freely into a large pharyngeal crop; trophi uncinate projecting freely into the crop. Kidneys often united by an anterior cross-piece. Body-wall often containing a definite system of canals, filled with refractive granules, and serving by their contraction to {221}dilate the disc. Males (Fig. 107, 1) and larvae vermiform with a ciliated pedal cup, and a simple wreath, with two eyes on the disc. Fam. 1. Flosculariidae: _Floscularia_ Oken, _Stephanoceros_ E. (Fig. 115). Fam. 2. Apsilidae: _Apsilus_ Metschnikoff (Fig. 112, A), _Acyclus_ Leidy, _Atrochus_ Wierzejski (Fig. 112, C). The family Flosculariidae contains some most exquisite forms; _Stephanoceros_, the "Crown Animalcule," being probably the most lovely of the Class, and many of the Floscules coming not far behind. The Apsilidae are mostly mud-dwellers. ORDER II. MELICERTACEAE.—Females (except in _Trochosphaera_) attached or tubicolous; tube variable. Disc with a dorsal gap (except _Conochilus_) often two-lobed or corolla-like; a ventral lip often separating off a ventral ciliated cup continuous by a pair of gutters with the ciliated groove; trochus of stronger cilia than the cingulum. Trophi malleoramate in a distinct mastax. Intestine much curved dorsally, cloaca long eversible (except _Trochosphaera_). Males and larvae as in Order I. [Illustration: FIG. 116.—_Melicerta ringens._ (After Joliet). A, Side view; B, dorsal view. _al_, Lateral antennae; _ci_, cingulum seen by transparency; _g_, gizzard; _p_, pellet in ciliated cup, about to be deposited on edge of tube; _tr_, trochus.] Fam. 3. Melicertidae: _Melicerta_ E. (Fig. 116), _Limnias_ Schrank, _Cephalosiphon_ E., _Oecistes_ E., _Lacinularia_ E., _Megalotrocha_ E., _Conochilus_ E., _Octotrocha_ Thorpe. Fam. 4. Trochosphaeridae: _Trochosphaera_ Semper (Fig. 118, D). The Melicertidae embrace a large number of tubicolous forms, many of which are social. This habit is especially noticeable in _Lacinularia socialis_, which forms a gelatinous incrustation easily seen by the naked eye; and in _Conochilus volvox_, which forms free-swimming globular aggregates, the young attaching themselves when hatched to the centre of the ball, and the ball splitting up into two as soon as undue pressure is exerted at the periphery by overcrowding. In this genus the eyes are very conspicuous in the adult, as they are in the similar free-swimming aggregates of _Lacinularia racemovata_.