322 



pliytes, the same tei'ms which Farre has given to tlie analo- 

 gous sets in the ciliobrachiates of the sea. 



" In Pakidicella then, three groups of muscles may be 

 detected. These are strictly analogous to muscles which 

 have been demonstrated in the salt water zoophytes of the 

 same order, and for a description of which, we are indebted 

 to an admirable paper of Dr. Farre, in the Philosophical 

 Transactions, an. 1837. The first of these groups to which 

 I shall direct your attention, corresponds with the anterior 

 set of retractor muscles of Farre. It may be observed (fig. 3 

 and 4, h, h) to take its origin from the internal surface of the 

 walls of the cell near the middle, and thence to pass upwards 

 in order to be inserted into the margin of the tentacular disk, 

 and upper part of the pharynx. The action of this group is 

 obvious, it is the true retractor apparatus of the polype, and 

 it is worthy of remark, that neither in this nor in any other 

 fresh water zoophyte whose anatomy I have studied, could 1 

 detect muscular fibres analogous to those described by Farre, 

 as inserted into the remote extremity of the stomach in those 

 zoophytes of the sea which had come under his observation. 



" The second set of muscles to be described in Paludi- 

 cella, consists of four bundles of fibres (fig. 3 and 4, i, i, i) 

 which arise from the inner walls of the cell near the top, 

 two at each side, having the tubular orifice between them. 

 From this origin, they pass towards the aperture of the 

 cell, slightly converging, and are inserted by distinct at- 

 tachments, which are all placed in the same plane, into 

 the inner surface of the tube near the margin of the orifice. 

 These ai'e in every respect analogous to the muscles which 

 Farre describes under the name of opercular, and to which 

 he ascribes the office of assisting in the inversion of the 

 polype tube drawing in its margin after the retreating po- 

 lype, and by their continued action, closing the orifice of the 

 cell. Reasons will presently be given for dissenting from 

 this view of the action of the opercular muscles, and in the 



