Victorella pavida of Saville Kent. 405 



towards the point wliere it joins the operculum (fig. 3, k). 

 This is a tube composed of a very delicate membrane, deve- 

 loped independently in a mass of protoplasm at the upper 

 part of the embryonic cell. It is generally described as com- 

 posed of set£e, around which the membrane is stretched ; but, 

 whilst I am not prepared to contradict the statements of such 

 authorities as Professor Allman and Mr. Pennington, not to 

 mention other writers on the subject, I am condnced, after 

 most careful observation directed to this special point, that 

 nothing of the sort exists in Victorella, nor can 1 find any 

 trace of setge with tlie highest power which I have found it 

 possible to use, about 500 diameters. When seen from above 

 the appearance is that of a circular opening, with zigzag 

 margin, no trace of thickening or unevenness being anywhere 

 visible. 1 have also examined specimens of Boioerhankia 

 imbricata and of Cylindroecium without being able to trace 

 the setge either with direct or dark-ground illumination, though 

 the very delicate setas on the tentacles were plainly apparent. 

 There are no muscles attached to the operculum ; but the 

 flexible portion of the tube below it is retracted by a powerful 

 muscle, whose fibres are striated, and which is attached below 

 to the rigid portion of the tube. There is also a muscle by 

 means of which the alimentary canal is retracted, and to the 

 base of each tentacle is attached a narrow band of striated 

 fibre (fig. 2, d), by which, in concert with its fellows, the 

 tentacular ring is withdrawn, and the action of one or more is 

 able to draw the crown to one side or the other. There are 

 also small muscles by means of which the animal is able to 

 rotate upon its axis. For the sake of clearness these muscles 

 are omitted in the drawing. 



In some cases a small projection may be seen upon the side 

 of the tube near its centre. This is the germ of a future 

 zooid, so that, in addition to the growth by enlargements 

 arising in the course of the stolon, each terminal zooid at 

 least may give origin to another colony, for the zooid thus 

 developed forms a stolon in the usual way. It should have 

 been stated, in speaking of the general stolon, that beyond 

 each zooecium there exists a septum in the course of the stolon, 

 through which the funiculus runs, having on either side of 

 the septum a conical enlargement, the bases of the two being 

 in contact. 



The nodal zooids are, as has been stated, generally much 

 smaller than the terminal and devoid of colour ; the tentacles 

 and stomach are also, as a rule, much less developed. Ana- 

 tomically, however, there is no difference between them. 



The interest attaching to this polyzoon no doubt centres in 



