\.VI Iln.Ml.lH s.K liiil (IA1NV1U.IA. Iti'.l 



itself. There may be as many as 6 medusa-buds upon one of these branches, and there are 

 usually several branches producing medusae. The buds are oval at first, but later they 

 become spherical. 



When set free the medusa's bell is only 0.3 to O.6 mm. wide, li is irregularly glob- 

 ular with very thick walls and an irregularly shaped bell-cavity. Tbeie are 4 penadi.il basal 

 bulbs, each of which gives rise to a single, marginal tentacle. These are long and lack ocelli. 

 4 simple, unbranched, oral tentacles, and 4 wide radial-canals, with an axial canal above the 

 stomach. The exumbrella is besprinkled with nematocysts as is usual in young medusx. 

 The tentacle-bulbs and manubrium are reddish-brown by reflected light. 



The hydroid is found at Helgoland attached to living or dead shells during the summer. 

 Both hydroid and medusa are described in detail by Hartlaub, 1897. 



Bougainvillia autumnahs Hartlaub. 



I'laU- id, figs. 4 and 5; plate 17, figs. 3 and 4. 



KI ROPKAN MKDI SA. 



Bottgainvillia autumnalis t HARTLAI B, iS^y, \\issen. Merrrsuntersuch. Knmmis. Mrrrr Kn-1, Hrlgnland, NVur Fnl^r, Bd. 2, 



p. 461;, taf. l <;, fign. 11-13. 

 Mti'gt'lii auturririuli), BROWNE, !9Od, Trans. Linnean Soc. London, ser. 2, Zoo]., vol. 10, p. 170. 



AMKRKAN MKDUSA. 



Bougainvillia gikbsi, MAYKR, 1900, Bull. Mus. Comp. Zool. at Harvard Collrg'-.. ?ol. ;-. p. ;. pl.ii>' 4. hi; 14, t v HAM. ITT, 

 1904, Bull. U. S. Bureau of Fisheries, vol. 24, p. 40; 1901, American Naturalist, vol. 35, p. 583. 



Bell rounded, 2.5 mm. wide, somewhat higher than a hemisphere, with thick, gelatinous 

 walls. 4 bulbous, rounded, marginal tentacle-bulbs, each of which gi\es rise to 3 to <i ten- 

 tacles. 4 narrow, straight radial-canals. Manubnum short, wide, 4-sided, urn-shaped; 

 not half as long as the depth of the bell-cavity. 4 oral tentacles which turn upwards and 

 branch dichotomously 2 to 5 times. The ends of the oral tentacles are simple, without terminal 

 knobs. 4 interradial gonads in the ectoderm of the stomach-wall. Tentacle-bulbs yellowish 

 to greenish-yellow. Manubrium green or brown. Hydroid unknown. 



Found by Hartlaub at Helgoland, German Ocean, from the end of August to the end 

 of November. Browne found it off the west coast of Ireland and in the English Channel. 



I consider this medusa to be identical with B. %ibbsi Mayer, of the southern coast of 

 New England. It is possibly separated by uncertain and variable color differences. A 

 description of the American form is herewith presented: 



Adult iiirJnm (plate 16, fig. 5; plate 17, fig. 4). Bell about 4111111. in height and 3.8 mm. 

 in diameter. Gelatinous substance very thick, so that the bell-cavity is only about hall as 

 deep as the height of the animal. There are 4 clusters of marginal tentacles which arise from 

 4 large, bulbous swellings situated at the bases of the 4 radial-canals. Each bulbous swelling 

 gives rise to 4 or 5 slender tentacles. There is a single, dark-brown ocellus at the base of each 

 tentacle upon the centripetal (velar) side. The velum is small. There are 4 straight, narrow 

 radial-canals. The manuhrium is wide and cruciform in cross-section, and the radial-canals 

 arise from the 4 coiners of the cross. The manubnum is short and docs not extend quite 

 half the distance from the inner apex of the bell-cavity to the velar opening. The mouth is 

 situated at the extremity of a short, tubular neck and there are no prominent lips. 4 radially 

 situated, oral tentacles arise from the sides of the neck of the manubrium. Each of these 

 branches dichotomously about twice. The gonads are developed upon the 4 interradial 

 sides of the stomach, and in the female the ova are large and prominent. The manubrium 

 is pearl-colored or of a delicate green. The entodermal cores of the tentacle-bulbs are red, 

 surrounded by a delicate yellow -green. The supporting lamella of the bell often displays a 

 faint greenish tinge. 



I'nniii; mi-iliisa. In the young medusa there are hut 8 tentacle.s, 2 from each tentacle- 

 bulb. The bell is a little higher than a hemisphere and the gelatinous substance is not very 

 thick, being of about uniform thickness everywhere, instead of being very thick at tin aboial 

 pole as in the adult. The manubrium is short and quadratic and there are 4 short, un- 

 branched, knob-shaped, oral tentacles. When the medusa is about $ mm. in height, the bell 

 is still hemispherical. The manubrium is wide, shallow, and quadratic, and the oral tentacles 

 branch once dichotomously. About } to 5 marginal tentacles arise from each tentacle-bulb. 



