RHaBDOPLEURA mirabilis. 29 



the spot from which the tentacular arms proceed. Immedi- 

 ately behind the anal aperture, between the terminal part of 

 the intestine and the dorsal wall of the gullet, which here 

 forms a little concavity, there appeared a clear cellular body 

 (fig. 1, r), in which several evident nuclei were visible. I 

 cannot, however, pronounce any decided opinion as to the 

 signification of this object ; it can scarcely be a nervous gan- 

 glion, as it does not lie in the substance of the body itself, 

 but only in the thin external skin which encloses the body. 

 The stomach and the intestine usually show in the living 

 animal a bright, opaque, yellowish- brown colour, which colour 

 seems mainly to be derived from the contents. When the 

 stomach and intestine are more empty, they shew a far paler 

 yellowish- white colour. The walls of both show plainly a fiue 

 cellular structure. 



It is evident that the digestive system in the Rhabdopleura 

 differs, in many points which have not been remarked by 

 AUman, from the normal system of the Polyzoa. In the 

 latter the stomach usually consists, as is well known, of two 

 distinctly separate parts, one shorter cylindrical cardiac part, 

 and a longer and wider pyloric part, which ends in a large, 

 rounded, bottle-shaped csecum (cul de sac). Therefore the 

 intestine usually takes its origin in these high up, or about 

 on a level with the transition of the cardiac part to the py- 

 loric part ; while in the Rhabdopleura, where no such divi- 

 sion of the stomach occurs, the intestine proceeds from the 

 posterior end of the stomach or fundus, as the immediate 

 continuation of the same. 



The tentacular corona or lophophore, situated in the 

 Rhabdopleura on the anterior end of the body, is of a totally 

 different appearance from that of the other marine Polyzoa, 

 while, on the other hand, it appears at first sight to show an 

 unmistakable resemblance to that of most freshwater Polyzoa 

 (P. HippocrepiaJ , and is also thus represented by Allman. 

 However, when it more closely examined, it displays many 

 essential differences, although by its strongly marked bilateral 

 symmetry, it appears to be most nearly connected with the 

 same, in respect of the semilunar or horse-shoe form peculiar 

 to them. 



As in the said freshwater Polyzoa, the lophophore or ten- 

 tacular frame does not form a circular ring, but is drawn out 

 into two lobes or arms, each of which bears a double 

 row of tentacles. These lobes or arms (fig. 5, &c., d), which 

 also here proceed from the dorsal side, are, however, consi- 

 derably longer and narrower, or more cylindrical than in any 

 other of the known Polyzoa; and while in those freshwater 



