Ill) 



MEDUS.E OF THE WORLD. 



Dissonema turrida Mayer. 



Plate 10, fig. l; plate 22, fig. I. 



Dissonema turriJa, MAYER, 1900, Bull. Mus. Comp. Zool. at Harvard College, vol. 37, p. 44, plate 2, figs. 3, 4; 1904, Mem. 

 Nat. Sci. Brooklyn Institute Museum, vol. i, p. 8, plate 2, fig. 10. 



Adult medusa. Bell bluntly cone-shaped with a hollow apical projection. It is 4 to 7 

 mm. high and the side walls are thin and flexible. There are 2 long, hollow, gradually tapering 



tentacles which are quite contractile, but 

 when expanded are 3 to 4 times as long as 

 the bell-height. Each of these tentacles has 

 a minute, red ocellus in the ectoderm of its 

 outer side near the bell-margin. In addition 

 to the two large tentacles there are 12 to 

 14 small, solid cirri which arise separately, 

 at equal intervals, from the bell-margin. 

 Each cirrus has a red ocellus in the ecto- 

 derm of its outer (abaxial) side at the bell- 

 margin. The velum is well developed. 

 The circular vessel is narrow, but the 4 

 radial-canals are broad, and the 4 convo- 

 luted, bag-like gonads occupy three-quar- 

 ters of their length and also lie upon the 

 adradial sides of the manubrium. In the 

 female each gonad contains 4 to 7 large eggs 

 which project prominently over the surface 

 of the organ. The manubrium is pyritorm 

 and the mouth projects beyond the velar 

 opening. The stomach-walls are thin and 

 flexible, and the mouth is surrounded by 

 large recurved lips with crinkled edges. 1 he 

 entoderm of the manubrium and tentacles 

 is a delicate green and the genital organs 

 and circular canal are tinged with green or 

 pink. The ocelli are red. 



In young medusae there are but 2 large 

 tentacles and 2 cirri. There are 8 ocelli. 

 The 2 long tentacles have tapering, hollow 

 basal bulbs, but their main shafts are at 

 first solid, though later they become hollow. 

 This medusa is common on the surface 

 in the Bahamas and at Tortugas, Florida, 

 in summer. 



Dr. H. B. Bigelow shows as a result of 

 sectioning the medusa of Dissonema that the 

 gonads begin to develop upon the adradial 

 sides of the manubrium and later extend 

 outward down the radial-canals. This fact, 

 taken in connection with the abaxial ectodermal ocelli, the hollow tentacles, bell-apex, rudi- 

 mentary tentacles and general form of the medusa, make it evident that Dissonema is one 

 of the Tiarinne. 



Genus PANDEA Lesson, 1843. 



Pan/tea, LESSON, 1837, Prodrom. Monog. Meduses, No. 22 (not published); 1843, Hist. Zooph. Acal., p. 288. ACASSIZ, L., 



1862, Cont. Nat. Hist. U. S., vol. 4, p. 347. 

 Pantlepa, HAECKEL, 1879, Syst. der Medusen, p. 53. 

 Pandra, AGASSIZ and MAYER, 1899, Bull. Mus. Comp. Zool. at Harvard College, vol. 32, p. 160. HARTI.AI-B, 1892, Nachricht. 



kgl. Gesell. Wissenschaft. Univ. Gottingen, p. 21. MAAS, 1904, Result. Camp. Sci. Prince de Monaco, fasc. 28, p. 15. 

 Diantfa, Quov ET GAIMARD, 1827, Annal. des Sci. Naturelles, tome 10, plate 6. 

 .\'on Dianefa, LAMARCK, 1816, Hist. Anim. sans Vert., tome 2, p. 505. 

 Pandja, ZOJA, 1892, Boll. Sc. Paira, Anno 1891, Nos. 3, 4, 3 pp.; 1892, Annals and Mag. Nat. Hist., ser. 6, vol. 9, p. 409. 



(Deniiroclam dohrnii gives rise to a medusa resembling Pandea ?) 



Fin. 62. Dissonema saphenella, after Haeckel, 1879. 



