342 JAMES F. GEMMILIL 
fully opened, lined for a very short distance downwards from 
the margin by close-set columnar cells having the characters 
of ectoderm. Body of Hydranth: sometimes slender, 
elongated (1-7 mm. in length), sometimes short (0-9 mm.) or 
vase-shaped according to contraction, usually showing con- 
striction below hypostome, furnished with stinging cells 
near middle, merging insensibly into hydrocaulus, except in 
contracted condition, when junction becomes evident. 
Hydrocaulus: short but varying in length (1 mm. to 
1-7 mm.), often irregularly bent, evidently weak, unbranched 
except in giving off the stalk of a medusa bud. Hydro- 
rhiza: creeping, branching but not anastomosing, 0-1 mm. 
across (including perisarc). The distinction between hydro- 
caulus and hydrorhiza is not always sharply apparent. In the 
thicker parts of a colony hydrorhizae may intertwine, and 
leaving the surface of attachment become equivalent to low 
irregular branching hydrocauli. When, however, the hydro- 
rhizae are not too crowded they remain adherent and give off 
unbranched hydrocauli. Perisare: thin, wrinkled irregu- 
larly but not ringed, enclosing hydrorhiza and hydrocaulus 
and separate from these except at occasional points of 
‘anchorage ’, thinning away at distal end of hydrocaulus and 
fusing with ectoderm at base of hydranth which is entirely 
theea-less. Medusae: Gonophore production takes place 
from the beginning of February till the end of March. Parts 
of the colony were isolated, kept in filtered sea-water, and in 
course of time a number of young medusae were collected. 
The buds appear at the end of short stems arising from the 
hydrocaulus well below the base of the hydranth, each hydro- 
caulus only producing a single medusa. The medusa buds, 
especially at full size, are more elongated than the free medusae, 
but the characteristic shape is acquired during the period 
immediately prior to detachment when vigorous pulsations 
may be noted. The young medusae have four rather wide 
radial canals, four tentacles opposite these, four small tentacles 
or tentacle buds in the interradii, and no lithocysts or ecto- 
dermal ocelli (figs. 16, 17, 18). The bell is dome-like and 
moderately deep: the stomach is quadrangular and the 
