140 THE MEDUSAE. 



thirty-five ; the smallest, seventeen. Curiously enough this very small num- 

 ber was counted in one of the largest specimens, 42 mm. in diameter, whence 

 it appears that the number of these organs is not closely connected with the 

 size of the Medusae. Vanhoffen (: 02'') has found from twenty-three to forty- 

 seven per octant, the latter number in a specimen only 32 mm. in diameter. 

 According to Maas (: 05) a specimen in the "Siboga" collection 44 mm. 

 in diameter had from seventy to eighty tentacles per octant. The radial 

 tentacles show a constant difference in size from those between the radial 

 canals, as already noted by both Vanhoffen and Maas, the former being 

 about twice as long and as stout as the latter (PI. 34, fig. 2). In struc- 

 ture, however, both classes are alike. The tentacles are solid ; the en- 

 dodermic layer composed of chordate cells, the ectoderm layer crowded 

 with nematocysts. Since in all the large " Valdivia " specimens the tenta- 

 cles were broken short off, Vanhoffen failed to observe their most character- 

 istic feature ; this is that each tentacle consists of two portions, — a flexible 

 proximal region in which the endoderm cells are cubical, and a spine-like 

 distal part, in which the cells of the core are flat and tile-like. The latter is 

 so stiff as to be more like a bristle than an ordinary tentacle. These two are 

 sharply separated (PI. 34, fig. 11). In most cases the ectoderm layer is de- 

 stroyed ; in the few instances in which it persists it is densely crowded with 

 nematocysts (PI. 33, fig. 9). It appears from Vanhoffen's (: 02*") studies that 

 in this species, as in the genus Homoeonema, tentacles of very young 

 specimens do not show the separation into two regions characteristic of 

 adults. 



Marginal Clubs. — In large specimens there are three or four of these 

 structures per octant. They are free clubs (PI. 33, fig. 8), standing on the 

 bell margin, consisting of ectodermic sheath and a core composed of chordate 

 endoderm cells. None of the specimens, all of which are preserved in for- 

 malin, now contain any otoliths ; but from the large size of the distal endo- 

 derm cells it seems probable that one or two otocysts were present, as Maas 

 (: 06'') believes to be the case in Homoeonema racovitzae. 



The radial canals are extremely broad, the stomach flat and without 

 any trace of manubrium or definite lip. 



Gonads. — Vanhoffen has described these organs in the female as " lang- 

 elliptischen " (: 02'', p. 69) and containing about fourteen large eggs. In the 

 male (PI. 34, fig. 1) they are proximal and more circumscribed than he figures 

 them (: 02^ taf. 9, fig. 8). 



