A. \THOM Kill S.K KI.KI TIIKK1A. 



95 



Each tentacle bifurcates and is twice as long as the bell-diameter. The 2 terminal 

 branches end one in an adhesive disk, and the other in a large, knob-like cluster of nettle-cells. 

 These branches are not quite as long as the basal shaft of the tentacle itself. An abaxial 

 ocellus is found at the base of each tentacle. 



The medusa is hermaphroditic, and the sexual products arc developed in an ectodermal 

 brood-pouch above, but not connected with, the stomach. The cavity ol the brood-pouch is 

 connected with the bell-cavity by means ot 6 simple, interradial openings which alternate with 

 the 6 radial-canals. Sperm develops in the aboral, and ova in the oral ( lower) \\all of the 

 brood-pouch. 



Medusa-buds are also produced upon the exumbrella side of the ring-canal, and this 

 process is usually associated with the sexual reproduction. The terminal suckers of the ten- 

 tacles are orange or yellowish-brown. Stomach and canals yellowish. 



This medusa is found clinging to green sea-weeds oft the Atlantic coasts of Belgium, 

 England, and France, and is widely distributed in the Mediterranean. Graefte. 1884, found 

 it to be common upon Ulvu from July to September at Trieste, Adriatic Sea. The budded 

 medusse become sexually mature in 3 to 4 weeks. The planula larva creeps over the sea- 

 weeds. 



Detailed descriptions are given by Ouatrefages and Allman, and the best modern account 

 is that of Hartlaub, who discovered the remarkable character of the brood-pouch or ecto- 

 dermal gonad. 



FIG. 48. Eletithfriti difholiwa, after Hartlaub, in Xordischcs Plankton. 



The hydroid is Clavatella prolifera Hincks (see definition of the genus Eleutheria). 



Eleutheria dichotoma is apparently quite variable. The tentacles and radial-canals, al- 

 though normally 6, may range from 4 to 8. Haeckel, 1879, p. 106, designates these aberrations 

 as "subspecies, " and gives specific names to twelve of them, although a number of these 

 should he credited to Eleutheria claparcJu Hartlaub and its variations. 



Hartlaub finds that the ova develop into planula larvae within the brood-sac before being 

 set tree. 



Miiller, 1908, studied the origin and structure of the eggs of this medusa. The eggs are 

 small, numerous, and oval in outline, not amcrhoid. There is no visible distinction between 

 exoplasm and endoplasm. The ooplasma is a network of very fine fibers. There are num- 

 erous small yolk-granules. 



Eleutheria claparedii Hartlaub. 



Eleuthrria elafaredii, HARTI.AI-K, 1889, Zonl. Anzeiger, Bil. 12, p. 665; 1907, Noriitscln^ Pl.mkt"ii. Nr. 12, p. 129. fii;. 121. 

 EIrullifria dichotoma, CLAPAREDF., 1863, Bcobacht. Anat. und Entwicklungsges, \virhrllosrr Thicrr, p. 4. t.if. I, figs. 4-10. 

 SPAGNOLINI, 1876, Catalogo Acalefi Mediterraneo, p. 24, tav. 4, fig. 2. 



Bell 0.4 to 0.5 mm. wide, irregular in shape, usually more or less hemispherical (fig. 41; i. 

 A ring of nettling warts on bell-margin. 8 to 10 tentacles, irregularly arranged in reference 

 to the 4 to 6 radial-canals. A small abaxial ocellus at the base of each tentacle. The ten- 

 tacles are 3.5 times as long as the bell-diameter, and they bifurcate at their extremities; one 

 branch ends in an adhesive disk, and the other in a nettling knob. About (> or ~ medusa-buds 

 are produced upon the subumbrella side of the ring-canal and project into the bell-cavity. 



