142 MEMBRA.NIPORID.E. 



The curious tubular processes*, which have been sup- 

 posed to be ovicells, are often developed in enormous 

 numbers. They are irregularly distributed over the 

 zoarium, and frequently occur in groups. Mr. Couch 

 speaks of them as appearing in December, January, and 

 February ; but I have met with them in June and October, 

 and it seems probable that they are not confined to any 

 particular season. 



The polypides have about 20 tall tentacles, which form 

 a very graceful bell. They are sometimes furnished with 

 the ciliated intertentacular organ which occurs on M. 

 pilosa and other species. A colony in full health and 

 vigour affords a rare display of delicate structure, viva- 

 cious movement, and graceful form. 



* Ellis was the first to notice these bodies. " There are dispersed," he 

 says, " here and there, at regular distances over the surface, little trans- 

 parent, short, erect tubes ; but to what use I shall not pretend to deter- 

 mine, unless they are the ovaries." Ellis 8f Solander, Zooph. p. 18. Couch 

 describes them as "of a yellow colour, semitransparent, and filled with 

 minute yellow granules, which appear to be ova " ( Corn. Faun. pt. iii. p. 93). 



These processes are cylindrical, and consist of a perfectly transparent 

 chitinous tube, which is lined throughout by a brownish membranous sac. 

 The sac is frequently inverted towards the top of the tube. They are closed 

 above, and open into the cavity of the cell at the base (Plate XVIII. fig. 6). 

 They appear at first as a swelling on the front wall of the cell, sometimes 

 placed at one end of it, sometimes subcentrally. The zocecia on which they 

 are developed are frequently abnormal in shape, being roundish and much 

 larger than is usual. The processes attain a very considerable length. So 

 far as I have observed, there is no trace of a polypide in the cells to which 

 they are attached ; I have never seen any thing within them except a small 

 quantity of granular matter, and have been unable to obtain any clue to 

 their history. 



These bodies have been investigated by Nitsche, who describes the zooecia 

 on which they occur under the name of " tower-cells " (' Thurmzoocien '). He 

 is inclined to regard the latter as zooecia, originally normal, which, having 

 lost their polypides, instead of developing others, have undergone this curi- 

 ous transformation (" Ueb. d. Anatom. u. Entwickl. von Flustra membra- 

 nacea," Zeitsch. f. Wissensch. Zool. xxi. Bd. 4. Heft, pp. 64, 65). According 

 to this view they are merely abnormal growths. 



