16 



briefly enumerated by various authors, for instance Allman, Hyatt &c. others, as characteri- 

 stics of the Polyzoa in general, and which therefore are considered as essential marks most 

 intimately connected with the idea Polyzoa, the anomaly of this form becomes so striking, as 

 finally even to justify a doubt as to whether it really can be referred to the class of Polyzoa. 

 First and foremost stands the want of a so-called Endocyst or Mantle, which sharply distin- 

 guishes this form from all other known Polyzoa, all of which possess such an appendage. This 

 Mantle is so essential a component part of a Polyzoon that it is difficult to imagine one 

 without it. One would rather imagine the Ectocyst wanting, as this plays a far less important 

 part in the economy of the animal, generally remaining passive, and properly only serving as 

 a protection for the soft animal. The Mantle is likewise a characteristic for the Tunicates 

 and the Brachiopods, which two classes have also been united by M. Edwards with the class 

 Polyzoa, under the common appellation of Molluscoidse (Hackels Himatega or Mantle-animals). 



Next, and as a consequence of the absence of a real Endocyst, the retraction and 

 protrusion of the animal in the Rhabdopleura are effected in a manner totally different from 

 that of the genuine Polyzoa: it moves up and down in its cell without being attached to the 

 opening, not by imagination and ecntjination of the anterior part of the cell, and not l>y wend 

 sets of special separate muscles. 



The following remarks on the affinity of Rhabdopleura are from my Father's manu- 

 script notes: 



,,The Rhabdopleura shews in many respects an unmistakable resemblance to certain 

 Hydrozoa. Just as in these, the individual animals are not attached to the anterior part of 

 the cells (in the Polyzoa the anterior involved part of the Endocyst is attached all round to 

 the basis of the tentacular corona); the cells are therefore open, filled (not with the so-called 

 perigastric liquid, but) with the sea-water entering from without; and the aperture of the cell 

 is of a defined and invariable shape (while the cells of the Polyzoa are always closed by the 

 attachment of the Endocyst to the basis of the tentacular Corona, and have therefore no 

 proper opening; for what is called aperture is nothing more than the part of the cell through 

 which the animal passes in and out)." 



,,Moreover, the retraction of the animal, effected in the Rhabdopleura by means of tie 

 roitfraelilc cord, at the end of which the animal is suspended, coincides essentially with that 

 of theHydrozoa in which the part corresponding to that cord (,,the fieshy stalk or axis' : , .,the 

 intestinal canal" (Loven), ,,the branched or unbranched Coenenchym, on which the individual 

 animals are situated, and which is perforated by a canal-like continuation of the abdominal 

 cavity of the individual animals") is indeed usually less free (often in many places attached 

 to the wall of the cell) and possesses a less degree of contractility than in the Rhabdopleura. 

 but yet in some genera, f. ex. Grammaria, also nearly approaches the Rhabdopleura in these 

 respects. On the contrary, the Protrusion in the Rhabdopleura is effected in a peculiar man- 

 ner, and different from that of either Polyzoa or Hydrozoa, namely by a sort of crecpinf/, 

 executed by the preoral prominence (bucal shield) which appears to answer to the Epistome 

 in the other Polyzoa, although in these it must have an entirely different function.'' 



