JELLYFISHES 



137 



ORDER CUBOMEDUSJE 



C" Cube-medusce ") 



GENUS Charybdcea 



C. marsupialis. Umbrella square, flattened on top, and of firm 

 consistency. Four tentacles fall from lobes on the umbrella, and four 

 club-shaped eyes are in marginal notches. Plate-like egg-sacs follow 

 each side of the four radial canals. The bell is one inch in diameter and 

 about two inches in height. It is not found on the coasts of the United 

 States. 



ORDER DISCOMEDUSJE 



C" Disk-medtisce ") 



SUBORDER SEMOSTOMJE 



A. flavidula. Size eight to ten inches in diameter ; disk gelatinous, 

 transparent bluish-white, broad and comparatively flat, with a fringe of 

 short tentacles of even length around the margin ; margin broken by 

 eight notches, in each one of which is a club-like organ (tentaculocyst) con- 

 taining calcareous spots or eyes, which are hidden by lappets or hood- 

 like coverings ; groups of nerve- 

 cells also lie in the marginal 

 notches; radial canals branched; 

 manubrium very short, with 

 square mouth, which is sur- 

 rounded by delicate membranes, 

 or oral arms, each arm being 

 a folded membrane tapering to 

 a point. The edges of the mem- 

 branes are covered with lasso- or 

 stinging-cells. Four egg-sacs, 

 or gonads, are conspicuous in 

 horseshoe shape around the 

 center of the disk. The gonads 

 are pink in the males, and yellow 

 in the females. These medusae 

 swim in shoals, and are common 

 everywhere in summer. They 

 may be said to be annual ani- 

 mals, for they make their ap- 

 pearance regularly as free- 

 swimming medusae in the latter 

 part of April, when they may be 

 seen in immense numbers near the surface when the water is smooth and 

 the sky clear. At this time they are about an inch in diameter. They 

 grow rapidly, and by the end of June have attained their full size. At 



Aurelia flavidula, about one fourth natural size. 



