CONTRIBUTION TO KNOWLEDGE OP RHABDOPLEURA. 629 



XXXVIII, fig. 1. We distinguish first of all the polypide-stalk 

 or ''gymnocaulus^' from the polypide body. The ''gymnocaulus" 

 was called "contractile cord'' bySars, andwa's erroneously iden- 

 tified by Allman with the ''funiculus'' or posterior mesentery 

 of the Phylactolsemous Polyzoa. Allman was led to use this 

 term and to make this identification through the imperfectly 

 preserved condition of his specimens^ which led him to believe 

 that a body wall existed outside what is the true body wall of 

 Rhabdopleura^ adherent to the tubarium as is the body wall of 

 a common Polyzoon to its cuticular product the zooeclum. The 

 body wall of Rhabdopleura has not these relations, and the 

 polypide-stalk has no relation to the funiculus of other Polyzoa. 

 The " body " of the polypide (as opposed to the gymnocaulus) 

 presents us anteriorly with the buccal-shield or disc, a prse- 

 oral muscular expansion between mouth and anus. It occupies 

 the same position as the epistome of Phylactolsema and Pho- 

 ronis. It attains even more remarkable proportions in the 

 allied genus Cephalodiscus of Mcintosh than in Rhabdopleura : 

 it is active as a locomotive organ, serving apparently to raise 

 the polypide in its tube so that it may partially emerge from 

 the tube's orifice ; and also it is active as a secreting organ, 

 building up ring after ring at the mouth of the tube. The 

 forms assumed by the buccal-shield in various conditions of 

 expansion and contraction, as well as the distribution of pig- 

 ment upon its surface, may be gathered from Plate XXXVIII 

 and its explanation. It is covered with fine cilia, which occur 

 also on the lophophoral filaments, the rest of the surface of 

 the animal being devoid of cilia. Beneath the buccal-shield, 

 on that face of the body to which the stalk is attached, is the 

 mouth. A pigmented region of the body, immediately adjacent 

 to the mouth, may well be called the thorax (PI. XXXVIII, fig. 

 1, F.) . It is followed by a sac-like region, the epidermic cells of 

 which are mostly devoid of pigment, and consequently allow the 

 yellow colour of the intestine to show through. This region 

 may well enough be termed the abdomen (/.). The characteristic 

 Polyzoon-bend of the intestine can be traced in this region of 

 the body, and the anus (b) is placed on a papilla which projects 



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