43 GEORGE OSSIAN SARS. 



of the genuine Polyzoa; it moves up and clown in its cell 

 without being attached to the opening, not hxj invayination 

 and evuf/inaiion of the anterior part of the cell, and not by 

 several sets of special sejiarate muscles. 



The following remarks on the affinity of Bhabdopleura are 

 from my father's manuscript notes : 



The Bhabdopleura shows in many respect 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 en- 

 docyst 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 moi'c than the part of 

 the cell through which the animal passes in an and out).-" 



" Moreover, the retraction of the animal, effected in the 

 Rhabdopleiira by means of the contractile cord, at the end of 

 Avhich the animal is suspended, coincides essentially with 

 that of the Hydrozoa, in which the part corresponding to that 

 cord {' the fleshy 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 the Rhabdopleura, but yet, 

 in some genera, f, ex. Grammaria, also nearly approaches the 

 Rhabdopleura in these respects. On the contrary, the pro- 

 trusion in the Rhabdopleura is effected in a peculiar manner, 

 and different from that of either Polyzoa or Hydrozoa, 

 namely by a sort of creeping, executed by the preoral promi- 

 nence (buccal shield), which appears to answer to the epis- 

 tome in the other Polyzoa, although in these it must have an 

 entirely different function." 



On the other hand, the highly developed digestive system, 

 the presence of an anus, the juxtaposition of the mouth and 

 anus, and, finally, the bilateral lophophore, are all characters 

 peculiar to the Polyzoa, and entirely foreign to the Hydrozoa. 



It is clear that we have under observation in the Rhabdo- 

 pleura, a form of animal life which stands as it were in the 

 middle between the Hydrozoa and Polyzoa, or forms a tran- 

 sition from one to the other ; one of those " perplexing 



