Polyzoa Entoprocta and Ctenostomata. 21 
In the Victorellidae (fig. 2, B) this region is much more highly specialized and 
consists of three parts. Immediately below the valve there is a comparatively large 
oval chamber without muscle-fibres, but hned internally with a fine layer of horny 
substance. Below this there is a short muscular tube, the external wall of which is 
composed of close-set circular fibres, and finally a relatively long thick-walled glan- 
dular tube connects the muscular region with the pylorus. 
In the Hislopiidae (fig. 2, C) still further specialization occurs. Three parts can 
again be distinguished, but their arrangement and structure are very different from 
Fig. 2.— Diagram of the oesophageal and cardiac regions of the ahmentary canal in certain 
families of Ctenostomata. 
A. — PaludiceUidae. B. — Victorellidae. C. — Hislopiidae. D. — Vesiculariidae. 
c. — oesophageal valve m. — mouth, o. = oesophagus proper. p.= pharynx. s.= stomach, 
cilia are represented by depending sinuous lines, circular muscles by minute circles with a dot in the centre of each, 
and horny structures in solid black. 
the corresponding parts in Victorella. The outermost part, immediately below the 
valve, is a conical thick-walled but non-mus2ular ' • proventriculus." This opens 
directly into a spherical chamber of large size in which the outer wall is composed of 
very stout circular m iscle-abres, wliile the lining consists of a thick layer of horny 
substance that has in longitudinal section the appearance of a sharp ridge. The inner 
surface of this horny lining is perfectly smooth. In preserved specimens the spherical 
chamber has the appearance of opening directly into the pylorus, but if the living 
animal be examined in an expanded condition, it will be seen that a narrow ring 
intervenes, bearing very long and powerful cilia. It is this ring that I regard as a 
