DESCRIPTION OF GENERA AND SPECIES, 
GYMNOBLASTEA. 
Family BOU GAINVILLIDiE. 
Character of the Family. Trophosome. — Hydranths with conical hypostome, ten- 
tacles filiform in a single verticil. 
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Gonosome . — Gonophores, planoblasts or heclrioblasts. 
Stylactis, Allman. 
Stylactis, Allman, Ann. and Mag. Nat. Hist., May 1864 
Generic Character. Trophosome . — Hydrocaulus rudimental, being reduced to short 
tubular processes which spring at intervals from a creeping stolon-like hydrorhiza and 
support the hydranths on their summit ; byclrorhiza destitute of external ccenosarcal 
investment. Hydranths clavate, with a single circlet of filiform tentacles which surround 
the base of a conical hypostome. 
Gonosome. — Gonophores adelocodonic, borne by the hydranth at the proximal side of 
the tentacles, or by the creeping stolon. 
The genus Stylactis was founded for two Hydroids originally described by Sars , 1 who 
referred them to the genus Podocoryne. If, however, we accept the validity of the 
principles "which have more recently guided the limitation and systematic position of 
Hydroid groups, these tw 7 o species of Sars have really no claim to admission into the 
genus Podocoryne. The gonophores are adelocodonic and sedentary, while those of 
Podocoryne are medusiform planoplasts ; and while the creeping stolon of the two species 
described by Sars is destitute of a coenosarcal covering, that of Podocoryne agrees with 
Hydractinia in being overlaid by a naked fleshy extension of the coenosarc. 
To the two species made known by Sars I was enabled to add another from the 
Mediterranean , 2 and a fourth species has now been contributed by the dredgings of the 
Challenger. 
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1 Faun. lit. Norv., p. 7, 1846, and Middelhavets lit Fauna, p. 40. 2 Gymnoblastic Hydroids, p. 305, 1871. 
(zool. chall. exp. — paet lxx. — 1888.) Aaaa 1 
