llli 



MKIH'.S.-E OF THE WORLD. 



Fiu. 77. Turritopsis, f/>. (') = (0ceania polycirrha), 

 after Keferstein, 1862, Zeit. fur wissen. 

 Zool., Bd. 12, uf. 12, fig. n. 



Rittenhouse finds that during the early stages ot cell-division in Turritopsis the multipli- 

 cation is solely by mitosis, but that later, when the embryo becomes a mere irregularly arranged 

 mass of loosely-compacted cells, some of the nuclei divide amitotically. 



When about 50 hours old the elongate, oval larva ceases to swim through the water and 

 settles down upon its side on the bottom. The larva then becomes the hydrorhiza, or root, of 



the hydroid, and the first hydranth arises as a bud 

 from about the middle of its length. The tentacles 

 of the hydranth develop in indefinite whorls, with 

 4 tentacles in each whorl, the oldest tentacle being 

 nearest to the mouth. In the mature hydroid the 

 tentacles appear to be irregularly scattered rather 

 than being arranged in whorls. 



Turrrtvpsts should he reared under more natural 

 conditions than those of the ordinary laboratory 

 in order to determine whether the remarkable, irreg- 

 ularly formed embryos described by Rittenhouse 

 be normal or merely the result of pathological 

 states induced by adverse conditions; but Miss 

 Beckwith has recently shown that the cleavage of 

 Pennarta is normally irregular as is described by 

 Hargitt. 



Rittenhouse finds that when the embryo is in the loose-celled, morula stage it may be 

 divided into two masses, each one of which produces a normal planula larva of small size. 



Turritopsis (?j lata von Lendenfeld. 



Tuiritafsis lata, VON LENDENFELD, 1884, Proc. Linncan Soc. New South Wales, vol. 9, p. 588, plate 22, figs. 36, 360. 

 ( ? ?) Mrlirerla pleurostoma, PERON ET LESUEUR, 1809, Ann. du Mus. Hist. Nat., Paris, tome 14, p. 353. 



Mature medusa. Bell 3.5 mm. high, 3 mm. wide, with a low, dome-like, apical projection. 

 60 to 130 marginal tentacles about as long as the bell-height. These have well-developed 

 basal bulbs, and there is an ocellus on the inner (velar) side of the base of each tentacle. Velum 

 well developed. 4 broad, straight radial-canals. The manubrium is mounted upon a peduncle, 

 but von Lendenfeld does not state whether it be composed of vacuolated, entodermal cells or 

 of the gelatinous substance of the bell, and his figures are too vague to throw any light 

 upon this point. Until this is settled we can not determine the systematic position of this 

 medusa. The stomach is spindle-shaped, about two-thirds as long as bell-height. The 

 mouth does not extend to the velar opening, and there are 4 lancet-shaped lips which are 

 recurved and one-third as long as the manubrium. These lips have stalked nettling warts 

 on their margins. There are 4 protruding gonads on the stomach-wall, each one being 

 one-fourth spherical in shape. Gonads and entoderm of tentacle-bulbs intensely brown. 

 Ocelli red. 



This is the most abundant medusa in Port Jackson, New South Wales, during the Aus- 

 tralian summer and autumn. 



The young medusae have but 4 marginal tentacles. 



Genus OCEANIA, sens. Kolliker, Gegenbaur. 



Oceania (in part), PERON ET LESUEUR, 1809, Annal. du Mus. Hist. Nat. Paris, tome 14, pp. 344-347. 



Oceania, KOLLIKER, 1853, Zeit. fiir wissen. Zool., Bd. 4, p. 323. GEGENBAUR, 18^6, Zeit. fur wissen. Zool., Bd. 8, p. 223. 



KEFERSTEIN UND EHLERS, 1861, Zool. Beitr. Messina, p. 83. METSCHNIKOFF, 1886, Embryo). Studien an Medusen, 



Wlen, pp. 23, 25, etc., to 78. 



Turritopsis (in part), HAECKEL, 1879, Syst. der Medusen, p. 65. 

 (>)Modecria (young medusa), FORBES, 1848, British Naked-eyed Medusa-, p. 70. 

 Modteria-'r Callitiara, HAECKEL, 1879, Svst. der Medusen, pp. 47, 48. 

 Occania=CalIiliara, VANHOFFEN, 1892, Verhandl. Gesell. Deutsch. Naturf. Arztc, 64 Vers., Abth. Syst.. p. 121. 



The generic name "Oceania" of Peron and Lesueur has no definite modern meaning, 

 for it was applied to many medusae belonging to the Eucopidae, Tiarinae, Thaumantidae, etc. 

 In 1862 "Oceania" was restricted by L. Agassiz to apply to a genus of the Eucopidae, but 

 this same genus had already been named Phialidium by Leuckart, 1856, and thus Agassiz's 



