EE PORT OX THE HTDROIDA. 
53 
Gonosome. — Gonangia large, oviform, perfectly smooth, narrowing below into a short 
peduncle which springs from a point just below a hydrotheca, and terminates in a short 
and wide tubular prolongation which carries the circular entire orifice. 
Locality. — Station 135c, Nightingale Island; depth, 100 to 150 fathoms. 
Sertularia leioccirpa is a rather strong-growing form with large distant hydrothecEe, 
each borne close to the distal end of an internode, where the hvdrocaulus forms a well- 
marked geniculation. The joints separating the internodes are often obscure. The 
specimen has a height of about three inches, and springs from a small plexus of hydro- 
rhizal filaments, while the proximal end of the stem is for some distance destitute of 
hydrothecae. 
The gonangium is large, its height exceeding twice that of an internode. It is 
perfectly smooth, showing no trace of annulation or rugae. 
The perisarc is transparent and allows of a good view of the included soft parts, 
which are well preserved in the specimen. The hydranths have about fifteen tentacles, 
and in extreme retraction present a condition hitherto un noticed among Hy droids, the 
gastric cavity emitting then a lateral, long, hernia-like protrusion which extends from 
the base of the hydrant h to a point beyond the origin of the tentacular crown (fig. la). 
This remarkable condition gives to the body of the hydranth the appearance of being 
doubled on itself, and forcibly recalls the formation of the alimentary canal in a Polyzoon. 
The fleshy bands which extend from the sides of the gonophore to the walls of the 
gonangium were well preserved, and at their points of attachment to the gonangium 
were flattened out in a stellate fashion. The bands had often become broken away from 
their points of attachment, leaving these behind in the form of stellate cells (fig. la). 
Sertularia unilateralis, n. sp. (PI. XXV. figs. 2, 2a, 2b). 
Trophosomc. — Hydrocaulus many times pinnately branched, forming a dense tuft in 
which the ramuli are all directed towards one side of the colony. Hydrothecm alternate, 
borne close to the distal end of each internode, those of opposite sides lying in two 
different planes, adnate to the internode for about one-third of their height, epicauline 
side ventricose towards the base, margin divided into four strong teeth, and with a 
thickened rim. 
Gonosome. — Gonangia oviform, equalling in height about three internodes of the 
stem, attached by a short peduncle to the internode just below a hydrotheca, annulated 
for the greater part of their height, and opening by a tridentate terminal orifice. 
Locality.— Station 149, off Accessible Bay, Kerguelen Island; depth, 20 fathoms. 
Sertularia unilateralis by the profusion of its branches forms a dense tuft which is 
upwards of an inch in height, and in which the ramification is rendered remarkable by 
