Fig, 3. — Perradial section through the entire Medusa, five times the natural size. 

 Strong longitudinal and transverse muscular folds are visible in the interior of the 

 gastral cavity (gp), also eight gastral grooves (gr) between the eight adradial 

 ridges of the gastral wall. The eight radial canals (cr) open above into the gastral 

 cavity, by the gastral opening (go). Eight wide, folded genital sacs (sc) run 

 out from the proximal halves of the radial canals, and are fastened to the subumbrella 

 (nitr) by the vertical leaf-shaped niesogonise (or genital mesenteries, ivr). ug 

 Gelatinous substance of the umbrella, al Oral lobes, cc Circular canal, v Velum. 

 tm Freer margin of the velum. 



Fig. 4. — Subumbral view of the Medusa, seen from below, three times the natural 

 size (comp. PL III. tig 2). The outer thick-walled abaxial half of the broad 

 velum is separated by a deep circular furrow from the inner thin-walled half, which 

 projects like a folded oesophagus, vw Subumbral, ve exumbral surface of the velum. 

 cm Freer margin of the velum, aw Oral marginal with the lobial swelling, g Gastral 

 cavity. 



Figs. 5-8. — Four radial sections through the umbrella margin, slightly enlarged, 

 in four directly following meridian planes, at the four points indicated in fig. 10 

 by the letters ABCD. The radial section in fig. 7 (A) touches a sucking-cup of 

 the first size (xa), in fig. 8 (B) a sucking-cup of the second size (xb), in fig. 5 (C) 

 a sucking-cup of the third size (xc), in fig. 6 (D) a sucking-cup formed of many 

 smaller sucking-cups (xd). The following letters have the same signification in all 

 the figures : yt the endodermal chordal axis of the solid sucking tentacle, u the 

 gelatinous substance of the umbrella, e the exumbrella, cc the circular canal, du 

 its umbral, dw its subumbral endodermal epithelium ; dp glandular endodermal 

 tufts and folds of the marginal wall of the circular canal, mw muscular layer of 

 the subumbrella, gw ectodermal epithelium of the subumbrella, vw subumbral 

 epithelium, ve exumbral epithelium of the velum ; mv muscular layer of the velum ; 

 nc urticating ring, re nerve ring. 



Fig. 9. — Oblique tangential section through a portion of the umbrella margin, 

 slightly enlarged, cc arching of the circular canal between the projecting folds and 

 tufts, of its marginal wall (dp) ; n urticating epithelium, and d solid chordal axis 

 of several sucking-cups. 



Fig. 10. — Portion of the umbrella margin, seen from the outside, ten times the 

 natural size. Lettering, comp. figs. 5-8. er Radial rib of the exumbrella. 



Figs. 11, 12. — The lower, free half of the oesophagus, three times the natural size ; 

 fig. 11 interradial, fig. 12 perradial section, ak Perradial angles, al Oral lobes. 



