331 



again entreat the indulgence of tlie Academy, while I lay 

 before it my observations upon other not less interesting 

 parts of the structure of these curious animals."* 



Description of the Plate. 



Fig. 1 . Paludicella articulata ; natural size. 

 Fig. 2. Portion of the polypidome magnified. 

 Fig. 3. A cell with the polype exserted, 



a, a, a. The polype cell. 



h. The orifice of the cell. 



c. That portion of the internal tunic which is carried out by 

 the polype during its egress from the cell. 



d. The stomach of the polype. 



e. The rectum. 



f. The oesophagus. 



y. The crown of tentacula exserted and expanded. 



h, h. The proper retractor muscles of the polype ; they are 

 now relaxed, and carried out by the animal in the act of protrusion. 



i, i. Two of the four sets of opercular muscles, also in a state 

 of relaxation. 



k, k, k, k. The parietal muscles, preserving, by their contrac- 

 tion, the membrane c, in a state of tension, and thus maintaining the 

 exserted condition of the polype. 



• After the present account liad been written, I happened to meet with a 

 paper by M. Dumortier, in the Bui. Ac. Brx. an. 1835, on the Polype a Panache 

 of Trembley, a polype belonging to the order now under consideration, and for 

 which M. Dumortier constitutes a distinct genus under the name Lophopus, 

 characterized by the tentacula, being destitute of cilia. So remarkable an ex- 

 ception, however, would this character offer to that of the entire order, that I 

 cannot but suppose Dumortier in error ; an opinion in which I believe myself 

 fully born out by the phaenomena subsequently described by this naturalist, and 

 which are evidently the result of imperfectly observed cilia. 



Dumortier details, at considerable length, the anatomy of the zoophyte, and 

 has witnessed fibres corresponding wiih the retractor and opercular muscles 

 described in the present communication. His paper is well worth perusal, though 

 some of his statements will require further corroboration. 



