Fig. 1. — The entire Medusa, subumLral view, from below, in four quadrants, natura 

 size. In the middle we see through the oral cross into the central stomach. The first 

 quadrant (to the left, above) shows the repeatedly folded brachial curtains or the delicate, 

 thin-membraned extensions of the oral arms, thickly frilled at the edges. The whole 

 subumbral wall is removed in the upper half of the second quadrant (to the right, above) 

 so as to show the upper (umbral) gelatinous wall of the dichotomously branched coronal 

 pouches and lobe pouches, which are only separated by narrow, radial, cathammal ridges ; 

 the tentacles, which spring in large numbers between the dichotomous radial ribs of the 

 subumbrella, are visible in the lower half of the second quadrant. The third quadrant 

 (to the right, below) shows a complete gastrogenital pouch, which springs with a narrow, 

 interradial base between every two perradial oral pillars ; the frilled genital band is deeply 

 inserted in the distal bottom of the repeatedly folded evagination of the fundus of the 

 stomach. The tentacles are cut away at their base in the fourth quadrant (to the left, 

 below) so that we merely see their insertion in the deep radial furrows (between the pro- 

 jecting dichotomous radial ridges of the subumbrella). The four sense niches are visible 

 in the lower half of the figure ; they lie far from the umbrella margin on the deep velar 

 furrow, which separates the broad zone of tentacles from the marginal velarium (or zone 

 of fused marginal lobes). 



Figs. 2-7. — Different views of the sense clubs or rhopalia and the adjacent parts, 

 enlarged. 



Fig. 2.— A subumbral sense niche seen from below, slightly enlarged in the middle, 

 the lanceolate sense niche (on). The sense club (or) lies hidden in the middle of the 

 lanceolate sense niche (on), somewhat nearer its proximal margin ; it is surrounded on 

 either side by the labiate sense folds (of) which rise from the subumbrella (iv). 



Fig. 3. — Vertical tangential section through a sense niche (om) slightly enlarged. 

 or Sense club, of Sense folds, co Sense canal. cl Lobe canal, ug Gelatinous substance 

 of the umbrella, zw Gelatinous substance of the subumbrella. k Cathamma between 

 the subumbrella and exumbrella (fused plate), irq Ectoderm of the subumbrella. 



Fig. 4. — Oblique section through a sense niche (oh) from above and within, slightly 

 enlarged, h Cathamma (fused suture between the subumbral (ziv) and umbral (ug) 

 gelatinous plate of the sense folds, of), co Canal of the sense club (or). 



Fig. 5. — Vertical radial section through a sense club and its nearest surroundings, 

 greatly enlarged. co x Sense canal. co± Blind distal end of the sense club, oa its ampulla- 

 shaped enlargement, ol Otolites, q Ectoderm, w Subumbrella. z Supporting plate. 

 d Endoderm. du Umbral endoderm. dw Subumbral endoderm. ug Gelatinous sub- 

 stance of the umbrella. 



Fig. 6. — Vertical radial section through the distal part of a sense club, whose otolites 

 have been dissolved by acid, very much enlarged. Letters as in fig. 5. 



Fig. 7. — Oblique longitudinal section through a sense club, almost horizontal, greatly 

 enlarged. Letters as in fig. 5. 



