66 AMERICAN HVDEOIDS. 



CLYTIA BICOPHORA Agassiz. 



Plate 12, figs. 1-3. 



Clijtia (Trochopyxis) hicophom L. Agassiz, Cont. Nat. Hist. U. S., vol. 4, 1862, p. 304. 



Clytia hwophora L. Agassiz, Cont. Nat. Hist. U. S., vol. 4, 1862, p. 345. 



Clithia bicophora A. Agassiz, Proc. Boston Soc. Nat. Hist., vol. 8, 1862, p. 225. 



Clytia bicophora A. Agassiz, North Amer. Acalephse, 1865, p. 79. 



Epenthesis bicophora Haeckel, Syst. der Medusen, 1879, vol. 1, p. 184. 



? Epmthesis foHcata Fewkes, Bull. Mus. Comp. ZooL, vol. 9, No. 8, 1882, p. 298. 



Clytia bicophora Nutting, Hydroids of the Woods Hole Region, 1901, p. 343. 



Clytia bicophora Hakgitt, Synopsis N. A. Invert., Hydromedusse, vol. 2, 1901, pp. 381, 588. 



Trofhosome} — Colony consisting of unbranched and sparingly branched pedicels springing 

 from a creeping rootstock and attaining a height of about 4 mm. The unbranched pedicels 

 sometimes attain a length of 3 mm. Pedicels usually annulated at their proximal and distal 

 ends and bare thi'oughout their median portions. These pedicels are not infrequently branched 

 once and rarely branchings of the second order are found; but by far the greater number 

 are simple and their diameter is less than that of the rootstock from which they spring. Hydro- 

 thecse closely resembHng those of 0. johnstoni, but considerably smaller, being but half the length 

 of the hydrothecse of the latter species, of which, indeed, they are almost perfect miniatures 

 in form except in the possession of a simple instead of a complex diaphragm. Marginal teeth 

 rounded, 12 to 14 in number. The distal portion of the hydrothecal wall is thin and collapsible 

 and when the hydranth is retracted a number of longitudinal folds appear corresponding to the 

 number of the teeth. 



This is a feature that I have not seen in C. johnstoni and, in connection with the character 

 of the diaphragm, affords a structural character sufficient to separate the species. 



Gonosome? — Gonangia usually borne on the rootstock but sometimes on the pedicels, espe- 

 cially when they are branched, oblong ovoid in shape, with the distal end abruptly truncated 

 and with the walls deeply and regularly annulated as in C. johnstoni. The gonangia are about 

 2\ times as long as broad, and their diameter is just about equal to the height of the hydrothecse. 



Gonangial contents. — Developing medusae. 



Medusse. — The adult medusae, according to Alexander Agassiz,^ are hemispherical in shape, 

 \ inch in diameter, with 16 marginal tentacles, 8 Hthocysts, and 4 radial canals beneath which 

 hang the purse-like ovaries. Agassiz says that this medusa is hardly distinguishable from that of 

 Clytia johnstoni. 



Distribution. — This species is found on the New England coast from the Bay of Fundy to 

 Buzzards Bay. (Agassiz, Nutting, Hargitt.) 



After considerable hesitation, the writer considers it advisable to acknowledge the specific 

 identity of this form, which many writers, begiiming with Hincks, have considered to be identical 

 with the well-known European form, Clytia johnstoni. The diagnostic marks of Clytia iicophora 

 are the comparatively small size of the hydrothecae, the presence of a simple instead of a complex 

 diaphragm, and the tenuity of the hydrothecal walls. 



There is much uncertainty regarding the distribution of this form on account of its similarity 

 to the European species, it being extremely Hkely that it has been mistaken for the latter species 

 in some of the American records. 



' Description of a specimen collected by the writer at Woods Hole, Massachusetts. 

 ^ Description taken from another specimen. 

 3 North Amer. Acalephse, 1865, p. 78, fig. 110. 



