6 AETHUB DENDY. 



lower extremities. I shall speak of them as the "endo- 

 dermal canals. '^ 



The Gastral Cavity, — The main gastral cavity, then, 

 occupies only the interior of the proboscis, but is continued 

 upwards into the float in the form of eudodermal canals. 

 The lining membrane of the main gastral cavity is thrown into 

 numerous very prominent longitudinal folds, forming ridges 

 which project inwards (figs. 5 — 9, L.G.B.), and whose edges, 

 iu the contracted specimen, are very sinuous (fig. 6) . At a 

 short distance below the septum the gastral cavity widens 

 out somewhat, and the ridges almost die away. At the 

 junction of the septum with the outer wall of the gastral 

 cavity a prominent annular fold projects into the latter 

 (figs. 7,8, Ai^.). 



The Endodermal Canals. — Above the fold just men- 

 tioned, around the margin of the septmn, which is otherwise 

 imperforate, lie the openings of the eudodermal canals (figs. 

 7, 8, Op. End.). From the network which these canals form 

 on the inner surface of the wall of the float (figs. 5, G, 

 End. C.) short branches are given off outwards, which run 

 into the stolons J but the canals themselves have apparently 

 no communication with the tentacles (fig. 8). 



The Septum. — The septum which separates the main 

 gastral cavity from the cavity of the float is a thin but firm 

 membrane. As already stated, it is somewhat arched 

 upwards. Its two surfaces are both smooth, but to the 

 upper one are attached some of the supporting membranes 

 in the chamber of the float (figs. 5 — 8). It is, as already 

 stated, imperforate, except for the openings of the endo- 

 dermal canals, and in this respect differs from either of the 

 two "diaphragms" in the gigantic Branchiocerianthus 

 imperator, which in some respects certainly resembles our 

 hydroid.^ 



The Cavity of the Float. — The cavity of the float is 

 very spacious, but it is subdivided by numerous very thin, 



' Vide Miyajiina, 'Jouru. Coll. Sci. Imp. University of Tokio,' vol. xiii, 

 p. 2:i5, etc. 



