456 MEDUSAE OF THE WORLD. 



ioo mm. long, both being of equal length. Their entodermal cells form an axial row and are 

 highly vacuolated and continuous with the entoderm of the stomach. The entoderm on the 

 axial and abaxial sides of the tentacles is developed into powerful strands of longitudinal 

 muscles, serving to sweep the tentacles to and fro in an oar-like manner. After penetrating the 

 gelatinous substances of the bell, the root of each tentacle bends centripetally inward. 



A deep, narrow, peronial groove extends upward along the side of the exumbrella from the 

 velar margin to the base of each tentacle. At the bottom of this groove there is a thick strand 

 of ectoderm, which is continuous with the ectoderm of the tentacle and unites at the base of the 

 latter with the ectoderm of the subumbrella. The peronial strands 90 away from the ten- 

 tacular radii are not at the bottom of open furrows, but are covered over on the abaxial side 

 by the gelatinous substance of the bell, so that there are no furrows excepting in the radii of 

 the tentacles, and only a slight notch at the margin in the radii 90 away from the tentacles, 

 the exumbrella surface being smooth and entire over the non-tentacular peronia. There are 

 usually a few wart-like thickenings at intervals around the margin and these projections are 

 best developed in the 4 interradii, alternating with the 4 peronia. They are probably vestigial 

 tentacles and are not always present. 



There are sometimes as many as 32 sensory-clubs, 8 per quadrant, although there are 

 usually only about 8 to 16. They are mounted upon very slender stalks and each contains a 

 single, spherical concretion. At the base of the club is a swollen cluster of sensory cells bearing 

 long, hair-like bristles. There are no sensory tracts over the exumbrella above the clubs. 

 Velum well developed, with powerful circular muscles. There is a niche-like infolding of the 

 ectodermal wall of the subumbrella under the bases of the 2 functional tentacles. 



Central stomach quite flat and lenticular, the mouth being a simple round opening. 

 This central stomach gives rise to 8 radiating outpocketings, 2 between each successive pair 

 of peronial strands. These are almost rectangular with rounded angles and extend outward 

 about half-way from the periphery of the central stomach to the margin. The gonads are 

 developed in the ectodermal wall of the subumbrella under the 8 stomach-pouches, and in 

 large medusae they occur under the entire areas of the pouches and also form a continuous 

 ring near the periphery of the central stomach. 



The entoderm of the central stomach, pouches, and tentacles is either green or red, but 

 is very variable, some specimens being nearly colorless or milky. Green appears by reflected, 

 and red by transmitted, light. 



This variety is widely distributed over the tropical Atlantic, Pacific, Antarctic (Vanhoffen), 

 and Indian Oceans. Apparently it has not been taken in the Mediterranean. I have found it 

 at Tortugas, Florida, in July. (See text-figure 301.) 



The best descriptions are those of Browne, 1904, Maas, 1905, Vanhoften, 1908, and 

 Bigelow, 1909. 



Vanhbffen, 1908, reports the finding by the V aU'ivia of 7 specimens of this medusa, or of 



its variety mediterranea, from which he does not distinguish it, among icebergs in the Antarctic 



Ocean. As he states, Solmundella is the most widely distributed Narcomedusa known, ranging 



from the North Atlantic through the tropical Pacific and Indian Oceans to the Antarctic. 



Living at temperatures of 27 to -1° C, and in depths ranging from 1,500 fathoms to the 



surface. 



Solmundella bitentaculata var. mediterranea Haeckel. 



Plate 54, figs. I to 3; plate 55, fig. 4. 



Mginopsis mediterranea, MUller, J., 1851, Archiv. fur Anat. und Physiol., p. 272, taf. II (development).— Gegenbaur, 1856, 

 Zeit. fur wissen. Zool., Bd. 8, p. 266.— Leuchart, 1856, Archiv. fur Naturgesch., Jahrg. 22, p. 33, taf. 2, figs. 8, 9.— 

 Metschnikoff, E., 1874, Zeit. fur wissen. Zool., Bd. 24, p. 26, taf. 4, fign. 17-22 (development); 1886, Embryolog. 

 Studien an Medusen, Wien, pp. 23 (egg), 35 (segmentation), 61 (formation of entoderm), 100 (actinula larva), taf. 9, 

 fign. 1-30. 



Solmundella mediterranea, Haeckel, 1879, s .Vst. der Medusen, pp. 309, 348, 352; Ibid., S. mulleri. p. 352.— Dawydoff, 1907, 

 Zool. Anzeiger, Bd. 31, p. 119, 3 fign. (mesoderm of larva). 



/EgiBO/m'j mediterranea, Graeffe, 1884, Arbeit. Zool. Inst. Wien, Bd. 5, p. 360.— Maas, 1893, F.rgeb. der Plankton Exped., 

 Bd. 2, K.c, p. 54, fign. 1, 2 (development); 1905, Craspedoten Medusen der Siboga Expedition, Monog. 10, pp. 73, 

 75. — Woltereck, 1905, Verhandl. Deutsch. Zool. Gesell., 15 Vers., p. 113, fig. 9, (? fig. 1 1) (development).— Maas, 1906, 

 Expedition Antarctique, S. Y. Belgica, Medusen, p. 12, taf. 1, fig. 5; taf. 3, fign. 23, 24 (medusa from the Antarctic 

 Ocean). 



Mginella dissoncma, Haeckel, 1879, Syst. der Medusen, p. 340, taf. 20, fig. 16— Agassiz, A., and Mayer, 1899, Bull. Mus. 

 Comp. Zool. at Harvard College, vol. 32, p. 166.— Mayer, 1900, Bull. Mus. Comp. Zool. at Harvard College, vol. 37, 

 p. 66, plate 14, figs. 30 to 32. — Bigelow, H. B., 1904, Bull. Mus. Comp. Zool. at Harvard College, vol. 39, p. 261. 



