140 Proceedings of the Royal Irish Academy . 



not equally developed on all sides of the same animal. Margin tentaculate. 

 No visible cinclides. Colour in spirit — body whitish ; disc and tentacles 

 burl'. Disc fairly wide, thin-walled ; mouth slightly gaping, raised, with two 

 inconspicuous actinopharyngeal grooves. Radii prominent, corresponding to 

 the tentacles. Tentacles short and small, slender or fairly stout, tapering 

 and pointed or blunt and stumpy, with basal mesogloeal thickenings on the 

 aboral side in all cases. The swellings are sometimes very marked, sometimes 

 inspicuous "i almosl absent : fchey are Leasl conspicuous in the smallest 

 inien, and practically absent from the tentacles of its inner cycle. The 

 tentacles arc arranged in two marginal cycles only; their size is rather 

 irregular, and here and there very small ones are hidden between larger ones 

 which seem to have developed at their expense. In the largest specimen 

 tie- arrangement is 72 7_' = 144 ; the medium-sized one has less than 

 120 altogether. 



«.— (i) .'/ . The specimen dissected had six pairs of perfect 



mesenteries and two unpaired perfect mesenteries of i he second cycle, disposed 

 a- in G. \ itia well developed, and present on mesenteries of all 



cycles; filaments also present on all cycles. Theperfecl mesenteries havelarge 

 oral, but no marginal stomata. No visible gonads. In all i hen- arc five cycles 

 of mesenterii — the first four regularly developed— 6p. + 6p. + I2p. + 24p. — 

 the fifth very small, and, in dissection, only visible in the lowest part of the 

 body, and on the underside of the oral disc. In sections taken about the level 

 of the enterostome, these mesenteries are visible ae merely small parietal 

 muscles with few processes, hardly projecting beyond the endoderm. A 



typical section of a third-cycle mesentery show.- thick m gloea (PI. XVIII, 



- 14); ach side of the mesentery as it leaves the body-wall, arise a few 



moderately stout processes, the middle one- fairly high and branched on the 

 end ■ ie mesentery, weak on the other. Succeeding thi e 



processes, on the i of very low ones for some distance, 



and these suddenly iise in height to form a well-developed diffuse pennon. 

 It i-. of fairly even width throughout, dying off suddenly at both extremities, 

 and has processes which, although fairly stout, hardly give the "reversed" 

 effect which prevails in C. ■ ire high and well branched. The 



opposite surface of the mesentery to the pennon traight edging of 



fibres. The above remarks apply in general to other third-cycle mesenteries, 

 the rm of the pennon varying in different cases. The fourth-cycle 



mesente those of the third cycle, but the penm narrower 



and less eloped. _ enteries have stronger pennons than 



any of the -•■ typically end very abruptly al their distal 



margin (where also the pj reach their big /elopment), and taper 



