REPORT ON THE DEEP-SEA MEDUSiE. 27 



stage. As in all other Narcomedusse, the tentacles are solid and fastened in the 

 gelatinous substance of the umbrella by a peculiar " tentacle root." At the point of 

 insertion of the tentacle where the " root " runs into the gelatinous substance, both 

 tentacle and root are in continuous connection with the proximal end of the peronium, 

 whose distal end passes into the urticating ring of the umbrella margin. The muscle 

 and the nerve of the clasp, which maintain direct communication between the nerve ring 

 of the umbrella margin and the tentacles, run on the axial side of the peronium. We 

 may therefore say that the solid dorsally inserted tentacles are composed of three 

 essential parts, which join at the point of insertion, viz., (l) the tentacle filament or the 

 free projecting part ; (2) the tentacle root, which is enclosed as a support in the 

 gelatinous substance ; and (3) the peronium which maintains the connection with the 

 umbrella margin. The tentacle filament, or the free projecting part of the tentacle 

 (figs. 4, 6 1), shows precisely the same structure which we have already described in the 

 solid tentacles of the Pectyllidse. The endodermal axis, which originates from the endo- 

 derm of the circular canal, forms a cylindrical column and consists of a single row of 

 large, clear, discoid chorda! cells, lying one above the other like the coins in a rouleau of 

 sovereigns. The conical or carrot-shaped tentacle root (figs. 4, 6, Ir), a direct process 

 of the endodermal axis, projecting more or less into the gelatinous substance of the 

 umbrella, consists of similar cells. The point of it has a centripetal direction and lies 

 with its lower (umbra!) side on the upper (exumbral) side of the gastral pouch, which it 

 likewise serves to support firmly. A structureless septum divides it from the gelatinous 

 substance covering it, and from the adjacent endoderm of the vascular system. The 

 exodermal epithelium of the free tentacle filament, which consists partly of thread 

 cells, partly of sense cells, does not run from its insertion at the root, but passes con- 

 tinuously into the urticating epithelium of the peronium. The urticating cells, which 

 contain nematocysts, are tolerably ecpially distributed ; so are the sense cells, which 

 partly bear cilia or feeling bristles. At the club-shaped swollen distal end of the tentacles, 

 the spheroidal thread cells are more thickly accumulated, and the cilia of the sensitive 

 epithelium considerably prolonged so as to form a thick bunch (fig. 3). The part of the 

 insertion of the tentacle, where filament, root and peronium join, is surrounded as with a 

 collar by a thick semi-circular urticating swelling (figs. 2, 4, 6, n). 



The twelve auditory clubs of this species, as in all Narcomedusae, must be regarded as 

 " modified acoustic tentacles " (System der Medusen, p. 307). The four interradial 

 (primary) auditory clubs Avhich lie on the point of the four corona! lobes, are from two to 

 three times as large as the eight adradial (secondary) (fig. 4, oV). The free projecting 

 lithocyst is club-shaped, and sits with a thinner short stalk upon a flat roundish " audit ory 

 pad " (figs. 4, 6, 7, 8). The solid axis of each auditory club consists of three to four short, 

 broad, discoid endodermal chordal cells, of which the proximal is the smallest, and con- 

 tinuously connected with the endodermal epithelium of the annular canal. The distal end 



