168 



P O L Y Z O A 



in this way. The Chilostoraa include a large series of genera 

 arranged in the sections Cellularina, Flustrina, Escharina, and 



FIG. 13. A. Crencecium of Ct'isia ebnrnea, Lin., one of the Cyclostoma ; g, g, 

 tubular zocecia with circular terminal mouths; .r, ocecium, being a zocecium 

 modified to serve as a brood-chamber. 



B. Diagram of a single polypide of one of the Chilostoma in a state of expansion, 

 in order to show the position and action of the operculum. a, operculum, 

 a plate of thickened cuticle hinged or jointed to b, the main area of dense 

 cuticle of the antitentacular region known as the zocecium ; c, the soft-walled 

 portion of the polypide in expansion. 



C. The same zooecinm with the polypiile invaginated (telescoped) and the 

 operculum a shut down over the mouth of the zocecium. 



D. Operculum detached, and seen from its inner face, to show the occlusor 

 muscles d d. 



Celleporina. For the systematic description of the highly complex 

 and very varied colonial skeletons or ccencecia of the Gymnola;uia, 



Fro. U.KinelosHas (ITaresia) ci/nllnis (from Sir Wyville Thomson). The poly- 

 pidea and zocecia are allied toSuffttla, but the zoarium as a whole is remarkable 

 for its definite shape, consisting of a number of slightly branched gracefully 

 bending filamenls supported like the leaves of a palm on along transparent 

 stalk. (See Husk, in Quart. Joarn. jlficr. <., 1X81, for further details.) 



the reader is referred to the works of Busk (9), Hincks (10), Sinitt 

 (11), and Heller (12). See also Ehlers (13) on Hypophorella. 



Sub-class 2. Entoprocta, Nitsche. 



Eupolyzoa in which the anal aperture lies close to the 

 mouth within the tentacular area or lophophore. Lopho- 

 phore sunk within a shallow basin formed by the inversion 

 of the broad truncated extremity of the cup-shaped body. 

 Tentacular crown not further introversible, the individual 

 tentacles (as in the Pterobranchia and unlike the Ecto- 

 procta) capable of being flexed and partially rolled up so 

 as to overhang the mouth (see fig. 15, B and C). Body- 

 cavity (ccelom) almost completely obliterated. The anti- 

 tentacular region of the polypide's body is drawn out to 

 form a stalk similar to the gymnocaulus of the Pterobran- 

 chia. The extremity of this stalk is provided with a 

 cement gland in the young condition which persists in the 

 adult of some species (Loxosoma neapolitanum, fig. 16, 

 dis). Cuticular investment (zocecium) of the polypides 

 feebly developed. A pair of small nephridia are present. 



The Entoprocta consist of the marine genera Pedi- 

 celliua (fig. 15), Loxosoma (fig. 16), and probably the 



FIG. 15. A. Two polypides and buds of Pedicellina belgica, Van B. (after 

 Van Beneden); greatly magnified, a, the polypide-stalk of a fully developed 

 polypide ; c, that of a less mature individual; 6, a bud. All are connected by 

 a common stalk or stolon. B. and C. Two views of the body of the polypide 

 of Pedicellina (after Alhnan). a, cuticle ; b, body-wall ; c, permanently in- 

 troverted anterior region of the body; </, margin of the tentacular cup or 

 calyx thus formed; e, mouth; /, pharynx; tj, stomach; A, intestine; i, anus; 

 k, epistome or prse-oral lobe ; /, nerve-ganglion ; m, gonad ; , retractor 

 muscle of the lophophore ; o, lophophore. 



insufficiently known freshwater American genus Urnatella 

 of Leidy. To these must be added P>usk's new genus 

 Ascopodaria, as yet undescribed, based on a specimen 

 dredged by the " Challenger," showing a number of Pedi- 

 cellina-like polypides, carried as an umbel on a common 

 stalk of very peculiar structure. Pedicellina is found at- 

 tached to alg;e, shells, zoophytes, etc., and to the integu- 

 ment of some Gephyrrean worms (Xijnt/iat/i/n pimi'/atus) 

 and Annelids (Aphrodite) ; Loxosoma occurs on carious 

 worms, &c. Whilst the buds of Pedicellina remain connected 

 so as to constitute a colony, those produced by Loxosoma 

 are continually detached, so that the polypide is solitary. 

 Further, the cup-like body of Pedicellina is deciduous, and 

 frequently falls from the stalk and is replaced by new 

 growth. There is less distinction between body and stalk 

 in Loxosoma, and the former does not become detached. 

 Apparently a very important feature in the structure of 

 the Entoprocta is the absence of a body-cavity. This is, 

 however, more apparent than real. The Entoprocta are 

 true Ccelomata, but the ca-lom is partially obliterated by 

 the growth of mesoblastic tissue. The nephridia presum- 

 ably lie in a space which, small as it is, represents the 

 ccelom. See Harmer (18) for details. 



