240 TEANSACTIONS LIVEEPOOL BIOLOGICAL SOCIETY. 



lie beneath and are partly bounded by the radial nerves. 

 The circular water vessel (cwv) gives off branches (twv) 

 to each of the tentacles, entrance to the tentacle being 

 made on the inner side of the calcareous ring (cr) . Other 

 appendages of the circular water vessel are the madreporie 

 tube, or water tube, {w) and the single Polian vesicle (pv). 

 The former, a simple tube lined by (probably ciliated) epithe- 

 lium, is seated on the upper surface of the water vessel, and 

 its free end opens into the body cavity ; the latter, is also 

 tubular, and of great length, but its free end is imper- 

 forate. It depends from the lower face of the water vessel. 

 The intestine {i) though much sacculated and occasionally 

 bent upon itself, runs a practically straight course from 

 mouth to anus, being suspended from the dorsal interra- 

 dins by the mesentery (m). It is accompanied in its 

 course by the typical dorsal and ventral vessels (dv and vv). 

 The genital organ consists of two bundles of csecal tubes 

 (g) which lie one on either side of the mesenterial fold 

 which suspends the intestine. The main tube of the left 

 bundle joins that of the right by penetrating the mesentery. 

 A single duct is thus formed which, passing forwards in 

 close proximity to the water-tube opens by a single pore 

 between two, and just outside of, the ring of tentacles 

 (go). ' Attached to the fold of mesentery by which the 

 intestine is suspended, just at the point where it joins 

 the body wall, there occur a great number of funnel-shaped 

 bodies with strongly everted margins, and lined by ciliated 

 epithelium (PL XVI., fig. 1, cf). These are the " ciliated 

 funnels " of Semper. Each funnel is attached by its 

 pointed apex to the mesentery ; and in addition to those 

 borne by the intestinal mesentery, another series, appear- 

 ing to the naked eye as an irregular but quite continuous 

 line, occupies the middle of the interradius next on the 



