352 



BULLETIN OF THE BUREAU OF FISHERIES. 



This species resembles Hydractinia verdi Ritchie, "■ but he found three or four sporosacs on each 

 generative zooid and only three eggs in each. The spines in his species are better developed also. 



Hydractinia echinata (Fleming). 



Alcyonium echinatum Fleming, British Animals, 1S2S, p. 517. 



Hydractinia echinata Hincks, British Hydroid Zoophytes, 186S, p. 23. Allman, Ray Society, 1871, p. 345. 



Hydractinia polydina Agassiz, Coat. Nat. Hist. U. S., 1862, p. 227. 



Hydractinia echinata Hargitt, American NaturaUst, 1901, p. 310. 



Hydractinia polydina Nutting, Hydroids of the Woods Hole Region, 1901. p. 335. 



Trophosofflc. — Colony arising from a basal coenosarc which overlies a chitinous, encrusting plate. 

 Hydranths with great power of contractility and extensibilit}'. Thus they may appear long and slender 

 or short and stout. They are generally contracted in the preserved specimens. Tentacles vary much 



in number. The whorl may appear very defi- 

 nite or may be so irregular as to appear as 

 though there were several approximated 

 whorls. 



Gonosome. — The sporosacs, male and 

 female, in different colonies, are foimd on 

 special generative zooids which are devoid 

 of tentacles but instead have extensive bat- 

 teries of nematocysts. They are usually no- 

 ticeably smaller than the nutritive zooids. 



Other zooids. — At intervals among the 

 nutritive and generative zooids tJiere are 

 zooids which look much like the generative 

 zooids, except that they are much longer and 

 more slender and are devoid of sporosacs. 

 They are even more mobile than the nutri- 

 tive zooids and may even double on them- 

 selves to form spirals. They probably serve 

 for the defense of the colony. 



Near the outer margin of the colony still 

 other zooids may be found. They are even 

 longer than the spiral zooids, but they do not 

 possess the nematocyst batteries. They ap- 

 pear specially sensitive, and probably serve 

 for the sense of touch for the colony. They 

 are few in number and are likely to escape 

 notice, even in the living colony, unless they are in active movement. Unless preserved specimens 

 have been specially fixed they seldom show these zooids. 



Color. — Whitish to reddish. Female gonophores orange red or bright red. 

 Distribution. — Bogue Sound, on shells, 10 to 12 feet. 



Since the time when Agassiz, in his Contributions to the Natiu-al History of the United States, 

 described aspeciesof //v</racfiHmand called it//, polydina, there has been much discussion as to whether 

 this species is identical with the Britisli species H. echinata Fleming. Hincks placed the American 

 species with the British, but Allman separated them, accepting Agassiz's opinion, though, at the same 

 time, expressing grave doubts as to the propriety of doing so. Among American naturalists Hargitt 

 has followed Hincks, while Nutting has taken the opposite view. With the exception of Nutting, none 

 of these ever had specimens from both sides of the Atlantic to compare, and it would seem, therefore, 

 that his opinion should have the soundest basis. 



Fig. 10— //>'i/raf/i?na ec/;maia (Fleming). A. portion of colony, show- 

 ing nutritive zooids, defensive zooids. and sensory zooids, as well as 

 the basal spines; B, female generative zooids; C, male generative 

 zooids. 



a Hydroidsf rem Cape Verde Islands, 1907, p. 498. 



