LEPTOMEDUS.E — OBELIA. 247 



has 4 lips. The gonads are very small and oval and are near the middle points of the 4 radial- 

 canals, but somewhat nearer margin than stomach. Gonads and stomach faint yellowish- 

 brown or brown. These medusae lived more than a month in Browne's aquaria at the 

 Firth of Clyde, Scotland, the water in the aquarium being constantly stirred by the plunger. 



Obelia australis von Lendenfeld. 



Obelia australis, von Lendenfeld, 1884, Proc. Linnean Soc. New South Wales, vol. 9, pp. 604, 920, plate 43, figs. 19-22. — 

 Bale, 1888, Proc. Linnean Soc. New South Wales, ser. 2, vol. 3, p. 753, plate 12, figs. I, 2. — Farquhar, 1896, Trans. 

 New Zealand Institute, Wellington, p. 460. — Hartlaub, 1901, Zoolog. Jahrbuchern, Abth. Syst., Bd. 14, p. 367; Ibid., 

 1905, Suppl. 6, p. 580. 



According to von Lendenfeld, the stems of the hydroid are creeping and adnate to foreign 

 bodies to which the stem clings like a hydrorhiza. This creeping stem is about 12 to 16 mm. 

 long and bears erect hydranths 3 or 4 mm. high. According to Bale, however, the hydroid is 

 coarse, rigid, 25 to 37 mm. high, sparingly branched, with alternate hydrothecae. These 

 differences may be due to the influences of different environments. The hydrothecae are 

 mounted upon short, annulated pedicels. The reproductive calycles are elongate. 



Perisarc of hydrorhiza reddish-brown, stems and branches light-orange. Entoderm of 

 polypites brown. When set free the medusa resembles that of O. geniculata and has 24 ten- 

 tacles. The bell of the adult medusa is flat and always reversed. Size ( ?) There are 30 to 40 

 tentacles. 8 adradial concretions upon the sides of the tentacle-bulbs. Stomach wide, urn- 

 shaped, with 4 well-developed lips. 4 large gonads on outer parts of the 4 radial-canals. These 

 gonads are oval to egg-shaped, and widest near their outer ends. The sperm-cells are, 

 according to von Lendenfeld, of entodcrmal origin. 



Found in Port Jackson Harbor, New South Wales, Australia, and on the east coast of 

 New Zealand where it grows upon Laminar ia. The medusae are produced from May until 

 July. 



This hydroid may prove to be but a variety of Obcha Jtchotoma (see Hartlaub, 1905). 



Obelia pyriformis Verrill. 



Laomedia gelatinosa, Leidy, 185c, Marine Invert. N. J. and R. I., p. 6. 



Europe pyriformis, Agassiz, A., 1865, North Amer. Acal., p. 88, figs. 127-129. 



Obelia pyriformis, Haeckel, 1879, Syst. der Medusen. p. 176. — Verrill, 1873, Report Commiss. Fish and Fisheries for 1871-72, 



pp. 390, 727. — Hargitt, 1904, Bull. U. S. Bureau of Fisheries, vol. 24, p. 49. 

 ( ?) Laomedea divaricata, McCrady, 1857, Gymn. Charleston Harbor, p. 93. 



Hydroid and young medusa. — The stems of this hydroid are usually 75 to 125 mm. in 

 height. The tutts branch in a tree-like manner. There are no knees nor breaks in the uniform- 

 ity of the stems, nor are there any swellings at the places where reproductive calycles are 

 attached. The pedicels of the polypites are long and usually composed of 12 to 15 rings. 

 The hydrotheca is short and flaring and with a smooth edge. The polypites have about 

 30 long, slender tentacles, and the mouth is situated at extremity of a prominent proboscis. 

 The reproductive calycles vary greatly in shape. When small they are almost cylindrical with 

 rounded corners and a slight constriction in middle; as they become larger they grow more 

 pear-shaped; and finally they assume the shape of an elongate ellipsoid with a pointed distal 

 end, and 3 or 4 deep constrictions upon their sides. There are from 9 to 12 medusae developing 

 in each calycle at once. When set free the young medusae have 24 tentacles and 4 pear-shaped 

 gonads which are situated very near to the manubrium. 



This species is found growing upon wooden piles and upon eelgrass on the Massachu- 

 setts coast. It is remarkable for its brilliant phosphorescence. It extends southward to 

 Charleston, South Carolina. 



This hydroid is distinguished from 0. dichotoma solely by the pyriform shape of its 

 reproductive calycles, whereas those of O. dichotoma are conical. 



Alexander Agassiz. 1865. p. 91, would distinguish as O. divaricata a hvdroid similar to 

 O. pyriformis, but in which the medusae have 48 tentacles when liberated. 



It seems probable that Obelia pyriformis and "divaricata" are only environmental races 

 of Obcha dichotoma. (See text-figure 128.) 



