HYDROID ZOOPHYTES. 27 
-plan of regarding it as synonymous with “sarcotheca” and applicable only to 
perisarcal skeleton. The zooid which the nematophore envelopes (in the case of 
. Halecitum only very partially) appears to us to be a true dactylozooid, and we have 
not adopted the use of any of the terms 
‘ 
‘sarcostyle,” ‘‘ machopolyp,” “ sarcodal 
q 7? Re > warl x rq wa 
process,” etc., suggested by various writers. 
ce 
The occurrence of the gonothecee in “ coppinia” masses in our specimens of 
Talecium arboreum is a feature of some interest. The number of genera in which this 
grouping of the sexual zooids occurs is extending as our knowledge advances. 
The gonothece of the specimens of [alecium arboreum and IL. telescopicuin 
obtained by the ‘Challenger’ were not observed, but the gonothece of //. jlevile, 
II. dichotomum, IT. fastigeatum, H. beanii and HH. cymiforme obtained by the same 
ee 
expedition were not in “coppinia” masses. This peculiar grouping of the gonothecze 
is not, therefore, a character of the genus, but may indicate a method for the future 
rearrangement of the species into subgeneric groups. 
HALECIUM ARBOREUM. 
(Plate IV., figs. Dien 29") 
Halecium arboreum, Allman, ‘ Challenger’ Reports, Vol. XXIII. (1888), pl. iy., figs. 1-3. 
Localities.—The species is evidently abundant in McMurdo Bay, extending from 
shallow water to depths of 130 fms. 
W.Q., McMurdo Bay, February 20th and 28th, 1902;—20 fms. W.Q., Flagon 
Point, January 17th and February 23rd, 1903; 10-20 fms. W.Q., No. 6 hole, 
January 31st, 1903; 130 fms. W.Q., February 21st, 1902; 10 fms. W.Q., off 
cable, February 17th, 1904. Kast End of Barrier, January 29th, 1902; 100 fms. 
The specimens of this species consist of a number of robust colonies rising to a 
height of 300 mm. from a thick hydrorhizal plexus. A few small colonies from the 
east end of the Ice Barrier were found attached to the stems of Plwinularia, 
Hydrosome.—The hydrorhiza is a dense plexus of tubes exhibiting a tendency to 
be grouped together in polysiphonic bundles. 
The main stem is a thick polysiphonic hydrocaulus 10 mm. in diameter. 
The proximal branches are polysiphonic, like the main stem, and anastomose freely 
whenever they come in contact with one another. The distal branches are much more 
‘numerous and usually monosiphonic. The monosiphonie branches (fig. 27) alone bear 
the hydrothecee, but in some cases these branches still bear hydrothece after the 
addition of the first few strengthening tubes. 
The ramification of the distal branches is pinnate, and in other parts of the colony 
it is roughly, but not rigidly, flahbellate. 
The thickness and roughness of the stem and of the principal branches afford 
admirable support for the hydrorhize of other hydroids, a list of which will be found 
on page 1. 
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