2SS MEDUS.E OF THE WORLD. 



eighth to one-tenth as wide as bell-diameter, and about one-third as long as depth of bell- 

 cavity. The 4 gonads are linear and developed upon the outer halves of the 4 radial-canals, 

 not touching the ring-canal. Stomach, gonads, and tentacle-bulbs sulphur-yellow. 



Found in the Mediterranean, at Messina, Villafranca, and Naples. Quite common at 

 Naples during January, 1908. (See text-figure 152.) 



Metschnikoff, 1886, reared the hydroid of this medusa from the egg. The egg is 0.14 mm. 

 in diameter, and is laid between 9 and 10 in the morning in January. Segmentation is total 

 and equal, and a spindle-shaped, one-layered blastula is formed. The entoderm arises from 

 cells which migrate singly into the blastula cavity from the narrow hinder end ot the larva, and 

 which finally fill it with cells. The larva becomes ciliated and nematocyst-cells develop in the 

 ectoderm of its posterior end. 2 or 3 blastula; sometimes fuse and develop into a single, some- 

 what irregular planula. Sometimes the whole larva becomes attached, forming a hydrorhiza 

 from which the polypites grow out, but in other cases the larva becomes attached only by its 

 forward end, the hinder end developing into a polypite. The hydroid is a Cuspidclla quite 

 similar to that described by Hincks, 1868 (Hist. British Hydroid Zoophytes, p. 209, plate 39, 

 fig. 4). The oral cone of the polypite is, however, flatter and more dome-like than shown by 

 Hincks. The tentacles arise in a single zone, are filiform, all of about the same length, and 

 lack a basal web. The hydrothecae are cylindrical, wide, and elongate, and arise at intervals 

 from a linear, creeping hydrorhiza. The orifice of the hydrotheca bears a number of sharp- 

 pointed, triangular teeth which may be drawn together, thus closing the opening with a conical 

 diaphragm. The polypite may be extended beyond this opening, or withdrawn within the 

 hydrotheca. The reproductive calycles are unknown. 



Mitrocoma minervae Haeckel. 

 Mitrocoma mintrvx, Haeckel, 1879, Syst. der Medusen, p. 189. 



This medusa is possibly identical with Mitrocoma anna, but is said to have a flatter bell 

 and relatively larger stomach and lips. 120 to 160 tentacles, and the same number of litho- 

 cysts and cirri. Each lithocyst is an open fold of the velum containing 8 to 12 concretions in a 

 single row. 4 gonads, linear, developed upon nearly the entire lengths of the 4 radial-canals, 

 leaving a short length of the inner ends of the radial-canals free. Found off" the south coast of 

 Africa (Indian Cape Stream ?). Development unknown. 



Mitrocoma cirrata. 



Euchiloia, sp., Hertwio, O. und R., 1878, Nervensystem der Medusen, pp. 70, 72, 90, taf. 7, fign. 16, 17; taf. 10, fig. 13. 

 Mitrocomium cirratum, Haeckel, 1879, Syst. der Medusen, p. 182, taf. 11, figs. 9-11. 



( ?) Mitrocomium assimile (young medusa), Browne, 1905, Pearl Oyster Fisheries Gulf of Manaar, Suppl. Report No. 27, Roy . 

 Soc. London, p. 137, plate I, fig. 3. 



Bell nearly hemispherical, 16 mm. wide. 8 tapering tentacles hardly as long as bell- 

 diameter and with large basal bulbs, flanked on each side by 3 or 4 spiral cirri. 30 to 40 

 marginal warts, 16 lithocysts, each with 2 to 6 (usually 3) concretions. No cirri on bell- 

 margin except upon the sides of the 8 tentacle-bulbs. Velum narrow. 4 narrow, simple radial- 

 canals. Stomach short, urn-shaped, with 4 simple lips, and no peduncle. 4 spindle-shaped 

 gonads on outer halves of the 4 radial-canals not touching the ring-canal. 



Stomach, gonads, and tentacle-bulbs milky-yellow to brownish. The marginal warts have 

 black, ectodermal pigment. (See text -figures 153 and 154O 



Found in the Mediterranean, at Corfu and at Naples. Rare. 



Browne, 1905, describes a medusa from Ceylon of which he obtained only I specimen, but 

 which closely resembles M. cirratum, and may be a young stage of the latter. It is described 

 as being 2 mm. wide, 1.5 mm. high, with bell-walls fairly thick. Only 4 radially placed ten- 

 tacles with basal bulbs flanked by cirri. 20 to 28 marginal warts, 5 lithocysts, each with 2 to 3 

 concretions. Gonads on outer halves of the radial-canals, each parted longitudinally in the 

 middle by the radial-canal upon which the gonad is developed. Color yellowish and opaque. 



Further studies are required to determine whether this Ceylonese medusa may or may not 

 be identical with the Mediterranean form. Their general resemblance is very close. 



