2^ GEORGE OSSIAN SARS. 



(unless we should consider the glassy skin which closely 

 surrounds the digestive apparatus to be an endocyst), con- 

 sequently also no perigastric fluid ; and, further, the cavity 

 of the cells stands in direct communication with the 

 surrounding medium, without being closed at the aperture 

 by a skin connecting it with the animaFs body. The retrac- 

 tion and protrusion of the polypide is, therefore, not cftccted 

 as usual by in- and evagination, but in a totally different 

 manner, of which more hereafter. Allman has indeed (1. c.) 

 imagined that he has perceived a trace of a real endocyst of 

 the same nature as that observed in the other Polyzoa, but 

 he has quite certainly deceived himself. The polypide of 

 the Rhabdopleura lies quite free in the cell, and is only 

 attached to the colony by means of the contractile cord, 

 neither by any endocyst nor special muscles, as appears 

 clearly enough from the fact that when the contractile cord 

 is severed, the polypide can be taken entire and uninjured 

 out of its tube with the greatest .ease. 



From the anterior part of the body where the mouth is 

 situated, yet, as will appear in the sequel, not as usual in a 

 terminal position, but rather in a ventral situation behind the 

 peculiar oval prominence (the bucal shield), the gullet or 

 cesophagus, rather short, but wide, and furnished with thick 

 walls, proceeds right downward or backward to the stomach, 

 from which it is separated by an also outwardly apparent 

 constriction, and by a sort of internal valve (the cardiac 

 valve) . 



The stomach (f), which is simple, without any armament 

 of teeth or hard parts in its interior, and furnished with tole- 

 rably thin walls, is elongated, rounded cylindrically, slightly 

 and somewhat irregularly curved, with ventral concavity, and 

 in its anterior part, where it has its greatest breadth, only a 

 little wider than the gullet, and occupying about two 

 thirds of the celFs calibre. In the anterior half it is of 

 about uniform thickness, but diminishes towards the pos- 

 terior end (pylorus) very rapidly, and goes imperceptibly 

 over, after turning a little to one side, into the intestine, sud- 

 denly curving itself upward and forward. The intestine (g), 

 which is not by any constriction, nor yet by any interior 

 valve (pylorus-valve), distinguished from the stomach, of 

 which it forms the immediate continuation, is narrow, cylin- 

 ^drical (its thickness scarcely one third of that of the stomach 

 in the widest part), only slightly tapering towards the end 

 (see fig. 3), and has a tolerably straight course forward, 

 lying close to the dorsal side of the stomach and gullet, and 

 terminates with a circular anal aperture, situated just behind 



