148 



MKDUS.E OF THE WORLD. 



entoderm is solid and composed of chordate cells. There is an ectodermal ocellus on the velar 

 side of each tentacle-bulb. Velum well developed. Well-developed circular muscles in the 

 subumbrella. There are 4 jagged-edged, slender radial-canals and a simple ring-canal. 

 The stomach is flask-shaped, cruciform in cross-section and mounted upon a short, pyramidal, 

 4-sided peduncle. This peduncle is a solid, gelatinous, truncated pyramid, only about one- 

 third to one-fifth as long as the stomach itself. It is not vacuolated as in Turntopsis. The 

 4 lips are large and recurved and extend to the middle of the bell-cavity and their edges are 

 studded with a single row of knob-like nematocyst-warts. The 4 gonads are developed upon 

 the interradial sides of the stomach and are longitudinal swellings with smooth outer surfaces. 

 The stomach and gonads are yellow or brownish-yellow. Eggs pearly-white. Lips red- 

 dish-yellow, or port-wine colored. Radial-canals, ring-canal, and tentacles milky-yellow. 

 Ocelli reddish-brown (see fig. 91). 



Found in the Mediterranean. Ouite common at Naples. (See figs. 78-81.) 

 Vanhoffen (1902, Verhandl. Gesell. Deutsch. Naturf. Arzte, 64 Vers., Abth. Sitz., p. 121) 

 maintains that this medusa is identical with CuUtttara polyopthalma Haeckel of the Canary 

 Islands, and with this I am in accord, having seen many specimens of the living medusa at 

 Naples. Trinci, 1906, describes a medusa from Naples which resembles O. armata in all 

 respects excepting that he finds no ocelli. He studied preserved specimens, however, and 



FIG. 80. Oceania. "Callitiara polyophlhthalma 11 (Oceania armata), after Haeckel, 1879. 



the ocelli may have faded. As Gegenbaur states, the ocelli upon the inner sides of the tentacle- 

 bulbs recall the conditions seen in Bougainvillia, and oblige us to place the medusa among 

 the Margelinae. In the Tiarinae, on the other hand, the ocelli when present are always on 

 the outer, abaxial sides of the tentacle-bulbs. 



Gegenbaur (1854, Zur Lehre von Generationswechsel, p. 28, taf. 2, fign. 10-16) reared 

 the larva from the egg, and later Metschnikoft carried out a similar series of studies. 



Metschmkoft, 1886, finds that the egg of this medusa is milky-white and 0.28 mm. in 

 diameter. It is laid between 6 and j o'clock in the afternoon during December, in the Medi- 

 terranean. The segmentation is total, but not equal, and the resulting blastomeres form a 

 very irregularly shaped, i-layered mass, inclosing a large segmentation cavity. Finally, a 

 symmetrical, egg-shaped, ciliated, planula larva is formed. The planula attaches itself and 

 becomes a branched hydrorhiza, from which the spindle-shaped clava-like hydranths arise. 

 These develop in about 18 days after the egg is laid. The polypite has 13 tentacles arranged 

 alternately in 3 whorls. 



In its irregularly shaped larva and in its mode of attachment this medusa resembles 

 Turritopsis, to which indeed it is evidently closely related, the only distinction between 

 Turritopsis and Oceania being that in the former the peduncle is vacuolated and in Oceania 

 it is solid and gelatinous. 



