250 MEDUS.E OF THE WORLD. 



Obelia geniculate!, de Varenne, 1882, Archiv.Zool. Exper. et Generale.tome 10, p. 659, planche 35. — Bourne, 1883, Quart. Journ. 

 Microscop. Sci., vol. 23, p. 621 (origin of sex cells). — Weismann, 1883, Entstehung Sexualzellen bei Hydromedusen, 

 Jena. — Bale, 1884, Catalogue Austral. Mus., Sydney, Zooph., p. 59, plate 2, fig. 2. — Marktanner-Turneretscher, 

 1890, Ann. naturb. Hofmus.Wien, Bd. 5. — Bale, 1893, Proc. Royal Soc. Victoria, p. 99 (from Victoria, Australia). — Pictet, 

 1893, Revue Suisse de Zool., tome I, p. 24 (from Amboina, Malay Archipelago). — Hartlaub, 1894, Wissen. Meeresunter- 

 such. Kommis. Meere Kiel, Biol. Anst. Helgoland, ser. 2, Bd. 1, p. 171. — Farquhar, 1896, Trans. New Zealand Institute, 

 Wellington, vol. 28, p. 460 (found on coast of New Zealand). — Nutting, 1896, Journal Marine Biol. Assoc. Plymouth, 

 ser. 2, vol. 4, p. 147; Bulletin U. S. Fish Commission, vol. 19, pp. 351, 380, figs. 38, 98. — Browne, 1897, Irish Naturalist, 

 p. 245. — Hilgendorf, 1898, Trans. New Zealand Institute, Wellington, vol. 30, p. 204, plate 17, figs. 2, 2a. — Hartlaub, 

 1901, Zool. Jahrbuchern, Abth. Syst., Bd. 14, p. 362 (from New Zealand). — Bedot, 1901, Revue Suisse de Zool., tome 9, 

 p. 430; Ibid., tome 13, p. 51 (literature cited to 1850). — Hargitt, 1902, American Naturalist, vol. 35, p. 382, fig. 18; p. 589, 

 fig. 55. — Torrey, 1902, University of California Publications, Zool., vol. I, p. 58 (from the coast of California); 1904, 

 ibid., vol. 2, p. 15. — Hartlaur, 1905, Zoolog. Jahrbuchern, Suppl. 6, p. 581, fig. D2 (coast of Chile, Straits of Magellan, 

 Falkland, Terra del Fuego, Kerguelen Islands). — Billard, 1901, Compt. Rend., Paris, tome 133, p. 441. 



(?) Eucope obliqua, Broods, 1881, Studies Marine Lab. Johns Hopkins Univ., vol. 2, p. 140; 1890, Handbook of Invertebrate 

 Zoology, p. 30, fig. 15. 



Obelia diaphana, Browne, 1902, Annals and Mag. Nat. Hist., ser. 7, vol. 9, p. 281. — Hargitt, 1904, Bull. Bureau of Fisheries, 

 U. S., vol. 24, p. 48, 1 fig. 



( ?) Thaumantias lucifera (iucida), Forbes, 1848, British Naked-eyed Medusa?, p. 52, plate 10, figs. 2a-g. 



Obelia lucifera, Browne, 1896, Proc. Zool. Soc. London, p. 481; 1906, Trans. Linnean Soc. London, ser. 2, Zool., vol. 10, p. 170. — 

 Bedot, 1905, Revue Suisse de Zool., tome 13, p. 140 (literature to 1850). 



( ?) Eucope polygena, Agassiz, A., 1865, North Amer. Acalepha;, p. 86, fig. 126. 



Var. Eucope fusiformis, Agassiz, A., 1865, Ibid., p. 90, figs. 132, 133. 



Adult medusa. — Bell flat and disk-shaped, about 6 mm. in diameter. There are about ioo 

 stiff, slender tentacles, each about one-quarter as long as diameter of bell. Tentacles quite 

 straight, projecting radially outward from edge of disk, their outer surfaces covered with a 

 large number of spindle-shaped nematocyst-capsules; their cores are composed of a single row 

 of disk-shaped, highly vacuolated, entodermal cells, which project beyond the bases of the ten- 

 tacles centripetally inward into the gelatinous substance of the bell; each tentacle is thus 

 provided with a bulb-shaped "root" or insertion. 



The velum is extremely small and consists of a barely perceptible web stretching between 

 the bases of the tentacles. There are 8 adradial lithocysts, 2 in each quadrant. Each lithocyst 

 is a closed vesicle and contains a single, spherical concretion. The lithocysts arise from the 

 ventral side of the bulbs of 8 of the tentacles. There are 4 straight, narrow radial-canals and a 

 slender circular canal. The stomach is very short and provided with 4 prominent lips. There 

 is no peduncle. The 4 gonads are developed upon the 4 radial-canals. They are spherical and 

 usually found nearer the circular canal than stomach. In the female each gonad contains 

 4 or 5 large ova. Stomach, gonads, and tentacle bases have a slightly milky or yellowish color, 

 all other parts of the medusa being transparent. 



Hydroid and young medusa. — The stems of the hydroid arise from a creeping stolon 

 usually found growing upon seaweed near low-water mark. They are rarely over 25 mm. high, 

 are zigzag, and rarely branch. Stem is jointed at each of the flexures and thickened imme- 

 diately below them, so as to form a series of projecting knees or rests from which the pedi- 

 cels arise. The pedicels are short and usually consist of about 4 to 6 rings. They are inclined 

 at an angle of about 30 with main stem and taper slightly outwardly. The hydrothecae are 

 short, being nearly as wide at the aperture as they are long. They are nearly conical, with 

 slightly bulging sides and a smooth upper edge. The reproductive calycles are borne upon a 

 short stalk consisting of 3 to 4 rings. They are club-shaped and taper gradually from base to 

 outer end, where they are widest. A short, tubular orifice arises from the distal summit of the 

 calycle. Each gonangium bears numerous medusa-buds. 



The medusa, at the time of liberation, usually possesses 24 tentacles (occasionally 16) 

 and 4 gonads close to the sides of the manubrium. The young medusa is transparent and fre- 

 quently swims with the bell rim everted. As development proceeds, the tentacles increase in 

 number, becoming nearly 100, and the gonads migrate outwardly along the 4 radial-tubes, so 

 that in the mature medusa they often lie nearer to the periphery of the bell than to the 

 manubrium. 



Very common all along the northern coasts of Europe and the Atlantic coast of America, 

 north of the Carolinas. It is of world-wide distribution, having been found at Arru Islands, 

 Amboina, Malay Archipelago; Australia, New Zealand, coast of Chile, Terra del Fuego, 

 Straits of Magellan, Kerguelen, Falkland Islands, and the coast of California. 



