[179] THE HYDROIDS 1 97 



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. Hydrothecae 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. 



Gonosome. Unknown. 



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



FILELLUM. 



Trophosome. Stem a creeping, slender rootstock, parasitic on 

 other hydroids, often forming a reticulate structure. Hydrothecae 

 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 om 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 HALECIDsE. 



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 planulae, 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. x, p. 809, 1758. 



