270 MEDUS.E OF THE WORLD. 



tacles. The bell becomes relatively shallower and broader until in the adult it is flatter than 

 a hemisphere. 



This medusa is exceedingly abundant during the summer months along the New England 

 coast. During July to September the harbor of Eastport, Maine, is crowded with these animals 

 to such an extent that their bells nearly touch as they swim at the surface of the water. The 

 medusa is less abundant at Newport, Rhode Island, and is rare at Charleston, South Carolina. 

 A brilliantly colored southern variety (plate 34, fig. 5) is common at Tortugas, Florida. 



Points of distinction between this form and Clytia bicophora, which it closely resembles, 

 are stated in the description of C. bicophora. 



Some of the European species of Phialidium appear to display a wide range of variability 

 in number and arrangement of radial-canals, tentacles, etc., but in our P. languidum not more 

 than two or three individuals in a hundred depart in any meristic manner from the normal. 



I am inclined to believe that our American P. languidum may be identical with P. hcmi- 

 splnm'ca = (Thaumantias hemisphicrica Forbes, Phialidium temporarium Browne), of the 

 Atlantic coasts of Europe. The only difference appears to be that in the European medusa the 

 stomach, gonads, and tentacle-bulbs range from yellowish to brown or orange, whereas in the 

 American medusa they are milky, green, or pink, the usual color in our specimens from the 

 coast of Massachusetts being dull-milky or faint yellowish-brown. 



Murbach and Shearer record a medusa from Puget Sound, British Columbia, which they 

 consider to be identical with P. languidum, and this opinion is rendered the more probable by 

 the discovery by Calkins of a hydroid in Puget Sound which appears to be identical with 

 Campanulma. It is possible, therefore, that our American P. languidum may be of circum- 

 polar distribution. 



Phialidium buskianura Browne. 



( ?) Thaumantias thompsoni, Forbes, 1848, British Naked-eyed Medus», p. 49, plate 11, fig. 5. 



Thaumantias buskeana, Gosse, 1853, Naturalist's Rambles Devonshire Coast, p. 385, plate 22. 



( ?) Phialidium variabile, Claus, 1881, Arbeit. Zool. Inst. Wien, Bd. 4, pp. 23, 1 1 1, plate 4) figs. 34-38 (growth of the medusa).— 

 Hartlaub, 1894, Wissen. Meeresuntersuch. Komm. Meere Kiel, Helgoland, Neue Folge, Bd. I, p. 193 (common at Helgo- 

 land).— Trinci, 1907, Archiv. Ital. Anat. Embr. Firenze, vol. 5, p. 533, pi. 32-36 (development and structure of oocytes). 



Phialidium variabilis, Van Rees, 1884, Tijdschrift Nederland Dierk., Ver. Suppl., Deel. I, p. 589. 



Phialidium buskianum, Browne, 1896, Proc. Zool. Soc. London, p. 488, plate 16, figs. 6, 6a; 1905, Proc. Royal Soc. Edinburgh, 

 vol. 25, p. 771. 



This medusa resembles P. hemisphxricum, but its gonads are short, swollen, and oval 

 and are situated between the middle points of the 4 radial-canals and the bell-margin. In P. 

 hcmispharicum, on the other hand, the gonads are long and linear, and developed upon the 

 outer halves of the radial-canals. According to Claus this, or a very similar medusa, may 

 become mature with 16 tentacles and about 20 marginal lithocysts somewhat irregularly 

 placed between the tentacles. When 1.5 mm. wide the medusa has only 4 radially placed 

 tentacles and 4 interradial tentacle-bulbs, the latter being flanked by 8 lithocysts, as in the 

 young of Clytia volubilis. The 4 gonads appear as minute spherical vesicles peripheral to 

 middle points of the 4 radial-canals and quite near ring-canal. 



Claus found this medusa in the Mediterranean. I have seen many living specimens of it 

 at Naples during a visit to the Stazione Zoologica in the winter of 1907-08. Medusae 

 similar to the above, or with as many as 20 to 32 tentacles and 25 to 60 lithocysts, are abundant 

 off the Atlantic coasts of France, Germany, and Great Britain. They range in color from 

 milky-white to green to rusty brown and are distinguished by their short, swollen, oval gonads 

 near the middle of the radial-canals. 



While the Atlantic and Mediterranean forms are probably identical, we can not be certain 

 upon this point until their hydroids are discovered. I am inclined to regard P. hemisphatricum, 

 and P. buskianum as at most mere varieties, one of the other. 



A green-colored Mediterranean medusa which I consider to be identical with P. bus- 

 kianum is described by E. MetschnikofF, 1886 (Arbeit. Zool. Inst. Wien, Bd. 6, p. 242, taf. 22, 

 fign. 11-14, l6 5 Embryol. Studien an Medusen, pp. 23, 36, 52, taf. 2, fign. 13-20, 24; tat. 3, 

 fig. 9). 



MetschnikofF states that this medusa is smaller and its gelatinous substance thicker and 

 more rigid than in P. flavidula( = P.hemispha-ricum). Bell not more than II mm. wide. There 

 are about 30 tentacles and 35 to 40 lithocysts on margin between tentacles. Thus there are 



