REPORT ON THE HYDROIDA. 
3 
Eudendrium, Ekrenberg (in part). 
Eudendrium , Ehrenberg, Corall. Rothen Meeres, p. 72. 
Generic Character. Trophosome . — Colony dendritic ; hydrocaulus invested with a 
well-developed perisarc. Hydranths with a trumpet-shaped hypostome, which is 
surrounded by a single verticil of filiform tentacles. 
Gonosome . — Gonophores adelocodonic, developed from the body of the hydranth at 
the proximal side of the tentacles, or from the sides of the hydrocaulus, monothalamic 
in the female colony, polythalamic in the male. 
The genus Eudendrium was separated by Ekrenberg from Tubular ia, with which it 
had been previously confounded. Its foundation as an independent genus is quite in 
accordance with its structural characters, though the grounds on which Ekrenberg believed 
himself justified in insisting on it are derived from characters comparatively trivial and 
destitute of generic value. The genus as defined by Ekrenberg accordingly contains forms 
which cannot be generically associated in a natural system. It was reserved for sub- 
sequent systematists, especially van Beneden and Strethill Wright, to indicate the true 
grounds of the revision, the most important of which, so far as concernsTke trophosome, 
are found in the trumpet-shaped hypostome with its single verticil of tentacles. 
Among the comparatively small number of Gymnoblastic Hydroids admitting of 
determination in the collection of the Challenger, are two species of Eudendrium — 
one a well-known European species, the other an undescribed species presenting some 
remarkable and distinctive characters. 
Eudendrium vestitum, n. sp. (PI. I. figs. 1, la). 
Trophosome . — Hydrocaulus slender, monosiphonic, much branched, branches alternate, 
dilated at the summit and with the perisarc extended over the base of the hydranths. 
Hydranths partially retractile within the dilated summit of the branches. 
Gonosome . — Gonophores (female ?) oviform, pedunculate, springing from the sides of 
the branches. 
Locadity. — Station 151, off Heard Island; depth, 75 fathoms. 
The specimen of Eudendrium vestitum contained in the collection forms a deuse 
tuft of slender profusely branched stems fixed to the detached spine of an Echinus, and 
attaining a height of about three-fourths of an inch. The branches are given off at a 
high angle and are remarkable for the way in which their chitinous perisarc is continued 
over the base of the hydranths, so that these when contracted have the appearance of 
being partly enclosed in a chitinous cup which recalls in some respects the hydrotheca of 
the Calyptoblastea. Here, however — a condition which has its parallel in certain 
species of Perigonimus and in some allied forms — the perisarc is adherent for a greater 
