REPORT ON THE HYDROIDA. 
81 
T\ e are here reminded of the genus Synthecium, in which the gonangia have an 
origin exactly similar to that of the branches in Thecocladium, the peduncle of the 
gonangium occupying in Synthecium the cavity of the hydrotheca, at the orifice of 
which it becomes tree in order to bear the o-onana-ium on its summit. 
o o 
Thecocladium jlabellum, n. sp. (PL XXXVIII. figs. 1-4). 
Trophosome. — Stems springing from one side of a rooted but otherwise free stolon- 
like tube, monosiphonic, much branched, branches alternate, all in one plane ; stems and 
branches closely set with hydrothecae. Hydrothecae alternate, tubular, tumid below, 
adnate to the hydrocaulus for nearly their entire height ; orifice circular and entire, with 
the margin continued for a short distance as a free, thin, membranous prolongation. 
Gonosome. — Gonangia springing each from a point just below the base of a hydro- 
theca, oboviform, annulated, terminating distally in a sessile, even orifice, and with a 
longitudinal furrow running along the epicauline side. 
Locality. — Simon’s Bay, Cape of Good Hope ; depth, 10 to 20 fathoms. 
Thecocladium jlabellum is the only representative as yet known of the remarkable 
genus to which it belongs. The stolon-like tube from which the stems arise sends off 
from distance to distance a cluster of root-fibres, but is free in the intervening spaces 
instead of being as in other Hydroids creeping and adherent throughout. It usually 
assumes an arched form, and from the convexity of the arch the stems arise at nearly 
equal intervals. The stolon is destitute of hydrothecse, but the stems carry them along 
their entire length. 
Soon after their origin the stems begin to give off pinnately disposed branches, which 
differ in no respect from the main stems except in being shorter. The branches as well 
as the stems all lie in the same plane, and this gives to the colony a somewhat flabelli- 
form habit, which, however, is not strictly maintained in the older specimens. The 
branches are sometimes prolonged by tendril-like, coarsely annulated extensions of the 
axis, which, uniting with neighbouring branches, contribute still further to the flabelli- 
form habit of the colony. These prolongations of the branches usually direct themselves 
towards the orifice of a hydrotheca, where they become attached, and are probably 
here in direct communication with the contents of the hydrotheca. 
The hydrothecse are very regularly alternate, and with their tumid bases give a 
slightly wavy outline to the stems and branches. Their distal ends are continued for 
a short distance by a delicate and easily torn membranous extension of their margin. 
The disposition of the branches is alternate and pinnate in accordance with that of 
the hydrothecse, out of whose orifices they extend themselves. They occur, however, at 
no regular distances, and there is nothing in the position or form of the hydrothecse 
(zool. chall. exp. — part lxx. — 1888.) Aaaa 11 
