TRACHYMEDUSjE — PTYCHOGASTRIA. 



373 



arranged. 3 long, filiform tentacles, which lack suckers, arise from the upper apex of the tri- 

 angular thickening, and there are also a large and variable number of short, sucker-bearing 

 tentacles, which arise from the basal parts of the triangular thickening. The long filiform ten- 

 tacles taper gradually from base to tip, but the short sucker-bearing tentacles widen outwardly, 

 and usually end in a pad-like sucker, though this is sometimes absent. There are probably 48 

 long, isolated filiform, suckerless tentacles, alternating with the 48 clusters of tentacles. Alto- 

 gether there are more than 1,000 tentacles. The "sucking cups" and "short-stalked tentacles" 

 of Haeckel, 1881, are only broken tentacles or basal remnants of tentacles, for they appear to 

 be quite brittle, as is commonly the case in Trachymedusae. 



There are 16 marginal sensory-clubs, 2 in each octant, arising from the inner side of the 

 bell-margin immediately under a group of sucker-bearing tentacles. The sensory-club is very 



Fig. 212. — Pt\chogaslria polaris, after Browne, in Bergens Museums Aarbog, 1903. 

 Above: Diagrammatic side view. Below: Diagrammatic cross-section of bell. 



small, mounted upon a short stalk, and contains a single concretion. There are 8 radial-canals. 

 These are not very wide upon leaving the stomach, but they widen outwardly and become very 

 broad and flat where they join the ring-canal. The ring-canal is also very broad and gives off 

 8 broad, flat, centripetal vessels which alternate with the radial-canals and taper to fine points 

 near the edge of the stomach. There is a thick layer of circular muscle fibers over the sub- 

 umbrella and the canal-system lies under this muscular system. 



Stomach about half as long as depth of bell-cavity, vase-shaped, 8-rayed above; each of 

 the 8 stomach pouches is bound to the subumbrella by a mesentery along the line of the cor- 

 responding radial-canal. Mouth-tube quadrate, with 4 lips; 4 of the stomach-lobes are in the 

 radii of the lips and 4 are interradial. There are 16 separated gonads along the sides of the 

 8 stomach lobes, on both sides of the 8 radial mesenteries. The gonads are not developed upon 

 the radial-canals, but are confined to the sides of the 8 rays of the stomach and completely 



