[179] THE HYDROIDS 



197 



Height of a fragmentary specimen about ^ inch. Stem and branches 

 sharply constricted proximally, composed of an axial tube which gives 

 off the eight or nine series of hydrothecae, and a number of peripheral 

 tubes enclosing the axial tube completely, thus burying all the hydro- 

 thecae nearly to their distal ends. Hydrotheca; arranged in about eight 

 or nine longitudinal series, forming spirals. The distal ends of the 

 hydrothecae are abruptly bent outward, so that the round, even aper- 

 ture is vertical. When the peripheral tubes are removed the hydro- 

 thecae are seen to be long, tubular, doubly curved, narrowing prox- 

 imally, but without true pedicels, and all springing from the axial tube. 



Gonosotiie. — Unknown. 



Distribution, — St. Paul harbor, Kadiak (Harriman Exped.). 



FILELLUM, 



Trophosome. — Stem a creeping, slender rootstock, parasitic on 

 other hydroids, often forming a reticulate structure. Hydrotheca 

 curved, decumbent, and partly adherent ; margin entire, without 

 operculum. 



Gonosome. — A ' Coppinia ' mass. 



FILELLUM SERPENS (Hassell). 



Campanularia serpens Hassell, Zoologist, No. 69, p. 2223. 



Filellum serpens Sars, Bidrag til Kundskaben cm Norges Hydroider, p. 29, 



1873. — Verrill, Preliminary Check-list Marine Invertebrates of Atlantic 



Coast, p. 17, 1879. 



Distribution. — Juneau, Alaska (Harriman Exped.) ; British Coast 

 (Hassell) ; Lofoten, Norway (Sars). 



Family HALECID^^. 

 Trophosome. — Hydrothecae reduced to the form of saucer-shaped or 

 collar-like hydrophores, usually borne on broad tubular pedicels ; 

 margins even, often reduplicated. Hydranths large, incapable of re- 

 tracting within the hydrophores, and with a conical or dome-shaped 

 proboscis. 



Gonosome. — Gonangia producing planula, and usually differing in 

 the two sexes. 



HALECIUM. 

 Trophosome. — No specialized defensive 'persons' developed. 

 Gonosome. — Female gonangia often surmounted by a pair of 

 hydranths. 



HALECIUM HALECINUM (Linn.). 

 Sertularia halecina Linn., Systema Naturae, Ed. .\, p. 809, 1758. 



