708 



MEDUSAE OF THE WORLD. 



The axial ducts of the 16 small, flapper-like, lateral scapulets connect directly with 

 the axial duct of the arm to which they are attached. The large, central stomach gives rise 

 to 16 main radial-canals which extend outward to the 8 sense-organs and to intermediate 

 points on the bell-margin. These 16 main radial-canals give rise to numerous side branches 

 which anastomose in a network of vessels as in Rhizostoma pulmo. There is no definite ring- 

 canal in the adult. 



The gelatinous substance of the medusa is translucent, dull, milky-yellow. The mouths 

 are rich yellow with chocolate-red blotches of pigment scattered at intervals at the bases of 

 the cirri. The ring-muscles of the subumbrella are a decided yellow, and according to Fewkes 

 the radial-canals are chocolate or rich chestnut in color. In the specimens studied by me, 

 however, they were yellow. The gonads are dull milky-yellow. There are numerous, small, 

 gastric cirri upon the gonads. 



FIG. 424. Rhopilema verrillii. Drawn^by the author from a specimen obtained by Professor Verrill at 

 Outer Island near Branford, Connecticut. 



Drawing one-half natural size. 6 of the mouth-arms are cut off close to their bases, and the scapulets are 

 cut off from 4 of them in order to show 2 of the subgenital ostia. The muscular arcades are 

 shown in one-half of the subumbrella and the canal-system in the other half. Thus in old 

 medusa? there are 16 partially isolated arcades of circular muscles as in Rhizostoma pulmo. 

 There are no radial muscles. 



This rare medusa was first found by Prof. A. E. Verrill, in 1886, in New Haven Harbor, 

 Connecticut, during September. In 1889, Professor Verrill again found it in considerable 

 numbers among the Thimble Islands about 10 miles east of New Haven, in Long Island 

 Sound, where they were common in August and September. They then disappeared, but 

 were again found at the Thimble Islands during the summer and autumn of 1903, and 

 again in Branford Harbor, Connecticut, in September and October, 1909. I secured the 

 specimen figured on plate 74 at Middleton, Pamhco Sound, North Carolina, in November, 



