752 Proceedings of Royal Society of Edinburgh. [sess. 
and has four perradial lobes which extend along the whole of the 
peduncle. Mouth circular. There are four oral tentacles which 
are twice dichotomously branched. Four narrow radial canals. 
The gonads are along the basal margin of the stomach and its 
lobes. Four perradial marginal groups of tentacles, each group 
with four tentacles ; the compound basal bulbs are globular and 
very small. Ocelli black and situated upon the basal bulb, one 
opposite each tentacle. 
Colour. — Basal bulbs reddish-brown. 
Size. — Umbrella 2’25 mm. in length and 2’5 mm. in width. 
Hybocodon prolifer, L. Agassiz. (Tables I. 1 ; II. 9. ) 
Amphicodon amphipleurus, Haeckel, 1879, p. 37, taf. i. 
Hybocodon prolifer, Browne, 1806, p. 466. 
In 1901, it was found during April and May, and it disappeared 
about the middle of June. There was a great shoal of Hybocodon 
prolifer in Loch Ranza, Arran, on 8th May. The shoal chiefly 
consisted of fine large adult specimens having three tentacles. 
Most of them had actinulse inside the cavity of the umbrella, the 
ova having developed up to that stage without breaking away 
from the wall of the stomach. Free floating actinulse were also 
common in the tow-nek 
In 1902, Hybocodon first appeared on 3rd April, and was last 
seen on 11th June. It was most plentiful during May. There 
was a shoal in tideway off the Laboratory on 5th May. Specimens 
with actinulse were taken on 12th May. 
The hydroid Hybocodon prolifer has not yet been found in 
British waters. To judge from the abundance of the medusa and 
the presence of free-floating actinulse, the hydroid is almost certain 
to live in the Firth of Clyde, probably in the neighbourhood of 
Arran. I think that it is absolutely necessary to see the liberation 
of the medusse from the hydroid to make sure of its identification. 
At Port Erin in 1893 and 1894 the medusse of Hybocodon prolifer 
were very abundant, but in 1896 not a single specimen was seen. 
I made a special search after the hydroid when it should have 
been breeding, but failed to find it. 
