34 



MEDUSAE OF THE WORLD. 



vals. The tentacle which is diametrically opposite to the long tentacle is tapering, and about 

 0.25 mm. long; while the 2 other tentacles are mere bulbs. The velum is well developed. 

 There are 4 narrow radial-canals, and a slender ring-canal. A long, slender, sinuous 

 canal extends from the aboral apex of the stomach upward into the apical projection of the 

 bell. In mature medusae the manubrium extends a short distance beyond the velar opening. 

 Ordinarily the mouth is a simple, round opening at the tapering extremity of the manubrium, 

 but when widely open, as in our figure, it shows 4 thick but not prominent lips. The genital 

 products are found in the manubrium, and in the female the eggs project from the surface of 

 the ectoderm. Entoderm of manubrium intense yellow-green and rose-color. Apical canal 

 intense yellow, often flecked with rose-color. The entoderm of the tentacle-bases is rose- 

 color and yellow, while the entoderm of the large annular swellings is rose-color. When 

 young the apical projection is not very high, the tentacles short, and without nematocyst- 

 nngs, and the manubrium short and tapering; not extending beyond the velar opening as 

 in the mature medusa. 



6. 



FIGS. 6 and 7. Sieenslrufia rubra. 



6. From life, by the author. Off Mousehole, Cornwall, England, October 23, 1907. 

 7. A. After Leuckart ("S. lineata"), 1856, Archiv. fur Naturgesch., Bd. 22. 

 B. After Spagnolini ("S. lineata"*), 1876, Catalogo Acalefi Mediterraneo. 



Found at Oregon Inlet, Pamlico Sound, North Carolina, in November, and at Beau- 

 fort, North Carolina, and Tortugas, Florida, in summer. It is apparently identical with 

 S. cranoides and S. lineata of the Mediterranean. 



Definite rings of nematocysts are not found upon the tentacles of the young medusa, and 

 are very variable in their development in mature specimens, some being profusely ringed 

 and some entirely unringed. Haeckel describes only unringed individuals from the Medi- 

 terranean, his specimens being similar to those found by me at Tortugas, Florida. 



I am inclined to believe that this Mediterranean and tropical American medusa will 

 prove to be identical with, or only a variety of, S. rubra of the Atlantic coasts of western 

 Europe. Certainly no differences, other than those well within the limits of common vari- 

 ability, can be detected between the medusae of S. rubra and S. lineata = S. cranoides; but a 



