304 



MEDUS/E OF THE WORLD. 



appears in winter. Graeffe identifies Haeckel's 0. gegenbauri with Linopsis campanula of 

 Claus, 1876. 



Browne, 1905, finds a medusa which appears to be identical with this species in the Gulf 

 of Manaar between Ceylon and India. 



The development of the Mediterranean medusa has been studied by MetschnikofF, 1886, 

 and Claus, 1 88 1. MetschnikofF finds that the egg is 0.14 mm. wide and is laid at 8 in the 

 evening in December. The segmentation is total, but not quite equal, and a hen's-egg-shaped 

 one-layered blastula is formed. The entoderm is formed from cells which migrate inward 

 into the central space from the narrow, hinder end of the larva. The planula becomes ciliated, 

 attaches itself by its forward end, and then the hinder end grows upward into a hydroid of 

 the genus Campanopsts. 



Claus was the first to discover the hydroid (Campanopsis), which he reared from the egg 

 in an aquarium. The hydrorhiza is creeping, open, and branched, and is found attached to 

 mussels or stones. The polypites are elongate, spindle-shaped, and arise singly at intervals 

 from the hydrorhiza. The mouth is at the extremity of a short, conical hypostome. There is 

 a single circlet of about 24 long, filiform, tapering, oral tentacles, which are united at their 



bases by a web. These tentacles bear 

 prominent nematocysts. The medusae bud 

 out singly from the sides of the polypite 

 below the zone of oral tentacles. Several 

 medusa-buds are seen at one and the same 

 time upon the sides of each polypite. 

 They are invested only by a thin perisarc 

 and are not produced within horny cap- 

 sules as in other Campanularian hydroids. 

 Indeed this interesting hydroid appears 

 intermediate in its characters between 

 Campanularian and Tubularian hydroids, 

 although it is probably merely a highly- 

 specialized and modified Campanularian 

 which has lost its hydrothecae and gonan- 

 gial capsules. 



When set free the young medusa is 

 about 1 mm. wide, with a thin-walled bell, 

 higher than a hemisphere. There are 

 4 simple, straight radial-canals without 

 gonads, 2 well-developed, radially placed 



'Octorchandra canariensh," after Haeckel, in Das tentacles, and 2 short tentacles 00° apart 

 System der Medusen=EK//ma campanulata. from the long ones. Each of the 4 



tentacle-bulbs bears a lateral cirrus, and in addition to these there are 4 small interradial cirri. 

 No peduncle. Stomach a mere short cylindrical tube. 



Eutima coerulea. 



Plate 41, figs. 4 and 5. 



EiraiM cmuUa, Agassiz, L., 1862, Cont. Nat. Hist. U. S, vol. 4, p. 362.— Agassiz, A., 1865, North American Acal., p. 112, 



fig. 163. 

 Irene carulea, Haeckel, 1879, Syst. der Medusen, p. 203. 

 Eutimalphes carulea, Mayer, 1900, Bull. Museum Comp. Zool. at Harvard College, vol. 37, p. 57, plate II, figs. 22, 22a. 



Bell is 10 mm. in diameter, a little broader than it is high. The gelatinous substance at 

 the apex of the bell is quite thick, but becomes progressively thinner as one approaches the 

 margin. There are about 32 short, slender, marginal tentacles, each flanked with a pair oi 

 small lateral cirri; also about 96 rudimentary tentacular swellings upon the bell-margin 

 there being usually about 3 of these swellings between each successive pair of tentacles. There 

 are 8 lithocysts, 2 in each quadrant, and each one of them contains 3 to 5 spherical concre- 

 tions. 4 radial-tubes. Velum well developed. 4 linear, slightly convoluted gonads. They 

 begin about half-way between the circular vessel and the peduncle and extend to a point 



Fig. 168- 



