370 MEDUSA OF THE WORLD. 



Craspedacusta, another fresh-water medusa, resembles Limnocnida in its tentacles and 

 lithocysts, but the mouth is 4-cornered and the gonads are upon the radial-canals. It seems 

 probable, indeed, that Craspedacusta is less highly differentiated than Limnocntda and repre- 

 sents a generalized ancestral state of the latter. If this be true, the mouth of Limnocntda has 

 become a round opening only secondarily and the gonads have only recently come to develop 

 upon the stomach-wall instead of on the radial-canals. 



Genus LIMNOCNIDA Gunther, 1893. 



Limnocnida, Gunther, 1893, Annals and Mag. Nat. Hist., ser. 6, vol. II, p. 274; '9°7» Vtoc. Zool. Soc. London, p. 643. — 

 Goto, 1903, Mark Anniversary Volume, pp. 17, 18— Gravier, 1907, Bull. Mus. Hist. Nat. Paris, p. 218. 



The type species is Limnocntda tatiganjica Gunther, of Lake Tanganyika and other 

 fresh waters of Central Africa, where it is abundant from April throughout the summer. 



GENERIC CHARACTERS. 



Numerous hollow tentacles which project from the sides of the bell above the margin. 

 Tentacles simple, without adhesive disks. Numerous (entodermal ?) sensory-clubs in inclosed 

 capsules on the exumbrella side of the velum under the outer nerve-ring. 4 (occasionally 5 or 

 6) radial-canals. Mouth .a round opening. Stomach-wall short and cylindrical. Gonads in 

 the ectoderm of the stomach-wall. Medusae are produced by budding upon the wall of the 

 manubrium. Sexual reproduction unknown. 



Gunther, 1893, 1907, sectioned this medusa and decided that the lithocysts were ento- 

 dermal, but Goto, 1903, reasoning only by analogy from his studies of Olindioides, casts doubt 

 upon this conclusion and believes that they may be ectodermal. Gunther would place this 

 medusa among the Trachymedusae, while Goto would classify it among the Eucopidae. 



The nearest ally of Limnocntda appears, curiously enough, to be Craspedacusta^ another 

 fresh-water medusa. In this form, however, the mouth has 4 principal lobes and the 4 sac-like 

 gonads are developed upon the radial-canals. 



Limnocnida tanganjicae Gunther. 



Tanganjicx (medusa of Lake Tanganjika), Bohm, 1883, Sitzungsber. Ges. Nat.Freunde, Berlin, p. 197. See also, von Martens, 

 Ibid. 



Limnocnida tanganjicx, Gunther, 1893, Annals and Mag. Nat. Hist., ser. 6, vol. 1 1, p. 269, plates 13, 14, 8 figs.; 1894, Quart. 

 Journ. Microscop. Sci., ser. 2, vol. 36, p. 271, plates 18, 19 (histology); 1907, Proc. Zool. Soc. London, p. 643, text-figs. 

 172-174, plate 37.— Moore, 1899, Proc. Zool. Soc. London, p. 291; 1903, The Tanganyika Problem, London, pp. 298- 

 308, 6 figs.; 1904, Nature, vol.69, p. 365.— Notes, 1904, Nature, Lon on, vol. 69, p. 348; Ibid., Moore, p. 365; 

 ibid., Cunnington, 1906, vol. 73, p. 310— Potts, 1906, Quart. Journ. Microscop. Sci., vol. 50, p. 623, plate 35, fig. 

 12— Browne, 1906, Annals and Mag. Nat. Hist., ser. 7, vol. 17, p. 304; 1908, J. S. Budgett Memorial Volume, Cam- 

 bridge, p. 471, plate 28, figs. 1-2. 



Limnocnida ( ?), du Guerne, 1893, Bull. Soc. Zool. de France, tome 18, p. 225. 



Limnocnida tanganyicr, Bernard, 1898, Bull. Mus. Hist. Nat. Paris, p. 62.— Gravier, 1903, Bull. Mus. Hist. Nat. Paris, tome 

 137, p. 867. 



Bell lenticular, nearly flat, quite thick at center, about 20 to 25 mm. wide. There are more 

 than 200 hollow tentacles of various lengths, there being when adult 8 or 9 orders of tentacles. 

 The radial, interradial, and adradial tentacles are the oldest and longest. There are no 

 swollen tentacle-bulbs, but the tentacles arise from the ring-canal and project outward from 

 the sides of the bell at some distance above the margin. The tentacles are adherent for some 

 distance, at their bases, to the surface of the exumbrella and are symmetrically arranged in 

 several series of alternating lengths. There are numerous nematocyst-warts, but no adhesive 

 disks upon the tentacles. There are about 250 irregularly arranged lithocysts, consisting of 

 closed capsules near the base of the velum upon the exumbrella side. Each lithocyst contains, 

 according to Gunther, a single spherical mass of entodermal cells attached by a stalk to the 

 side of the capsule nearest the ring-canal. These lithocysts lie under the outer nerve-ring. 



There are 4 (occasionally 5 to 7) short radial-canals and a simple ring-canal. Stomach 

 is two-thirds as wide as the bell and has short vertical sides, so short that the mouth does not 

 project beyond the velar opening. The mouth is a wide, circular space, always gaping open. 

 The stomach space is partially filled by a lenticular, gelatinous thickening. Medusa-buds 

 are produced in large numbers upon the outer side of the stomach-wall, both ectoderm and 



