68 



MEDUSA OF THE WORLD. 



All parts of the hydroid stock are highly contractile and the gonosomes and zooids are 

 without chitinous sheaths. 



The hydroid is colorless, but the medusa-buds are reddish and orange in color. The 

 terminal parts of the flask-shaped zooids are also pigmented with reddish-orange. 



A single stock of this hydroid was found by Fewkes in Narragansett Bay, Rhode Island, 

 attached to a fish, Seriola zonata, in August, 1887. The fish was swimming near the surface 

 and was apparently but little injured by the presence of the parasite. 



It is interesting to observe that Alcock, 1892 (Annals and Mag. Nat. Hist., ser. 6, vol. 10, 

 p. 207, I fig.), has discovered a hydroid of the genus Stylactis which is commensal upon a 

 fish, Minous inermis. This hydroid, however, produces no medusae. 



Genus EUCODONIUM Hartlaub. 



Eucodonium, HARTLAUB, 1907, Nordisches Plankton, Nr. 12, p. 71. 



The type species is Eucodonium brownei Hartlaub = Dipurena sp. Browne, from the 

 British Coast. 



GENERIC CHARACTERS. 



Codonidae with 4 equally developed, radially placed tentacles, each of which terminates 

 in a distal knob. Stomach mounted upon a gelatinous peduncle. Hydroid unknown. 



This genus is distinguished from Sarsia and Slabberia by the gelatinous peduncle upon 



which the stomach is placed. It is distinguished from 

 Dysmorphosa by the terminal knobs of its tentacles and 

 by its ring-like gonad. 



Eucodonium brownei Hartlaub. 



Dipurena sp., BROWNE, 1896, Proc. Zool. Soc. London, p. 473, plate 16, fig. 2. 

 Eucodonium brawnei, HARTLAUB, 1907, Nordisches Plankton, Nr. 12, p. 71, fig. 67. 



Bell pyriform, thin-walled, I mm. wide. 4 radially 

 placed, slender tentacles with small basal bulbs. Ten- 

 tacles twice as long as the bell-height and with scattered 

 nematocysts along their lengths, and each with a large, 

 swollen, nematocyst-beanng knob at outer end of tentacle. 

 No ocelli. Velum wide. 4 straight, narrow radial-canals. 

 Stomach short, mounted upon a conical, gelatinous 



from Europe, after Hincks in Brit- peduncle. Mouth a simple, round opening at about the 



level of the velum. Medusa-buds arise from the sides of 



the stomach. The tentacle-bulbs are blackish, stomach and terminal knobs of the ten- 

 tacles, dull dark-brown. Found at Plymouth, England, in September. Gonads( ?) This 

 is a young medusa, but we can not refer it to any known mature form. 



Genus ECTOPLEURA L. Agassiz, 1862 (sens, amend.). 



Tubularia dumortierl, VAN BENEDEN, 1844, Mem. Acad. Belgique, tome 17, p. 50, plate 2. 



Eclopleura, AGASSIZ, L., 1862, Cont. Nat. Hist. U. S., vol. 4, p. 343. AGASSIZ, A., 1865, North Amer. Acal., p. 191. HAZCKEL, 

 1879, Syst. der Medusen, p. 21. FEWKES, 1882, Bull. Mus. Comp. Zool. at Harvard Coll., vol. 9, p. 295; 1883, Bull. 

 Mus. Comp. Zool. at Harvard Coll., vol. n, p. 85, plate I, fig. II. ALLMAN, 1871, Monog. Tubul. Hydroids, p. 423. 

 HINCKS, 1868, British Hydroid Zooph., vol. i, p. 123. VANHOFFEN, 1891, Zool. Anzeiger, p. 443. HARTLAUB, 1894, 

 Wissen. Meeresuntersuch. Komm. Deutsch. Meere Kiel, Abth. Helgoland (l), Bd.l, p. 188; 1907, Nordisches Plankton, 

 Nr. 12, p. 93. BROWNE, 1905, Proc. Roy. Soc. Edinburgh, vol. 25, p. 748. 



This genus was founded by L. Agassiz, 1862, the type species being E. dumortieri which 

 was first described by Van Beneden, 1844, from the coast of Belgium under the name Tubu- 

 laria dumortien. 



GENERIC CHARACTERS. 



Codonidae with 2 or 4 simple, unbranched tentacles situated at the bases of 2, or of all, 

 of the 4 radial-canals. 8 longitudinal rows of nematocysts extend from the 4 tentacle-bulbs 

 over the surface of the exumbrella to the apex of the bell. The manubnum is short and blunt, 

 and the mouth is a simple, round opening. The hydroid is Ectopleura, and is closely 

 related to Tubularia. 



FIG. 33. Eucodonium brownei, after Browne, 



in Proc. Zool. Soc. London. 

 FIG. 34. Hydroid of Ectopleura dumortien 



