1912-13.] Hydroids of British Antarctic Expedition, 1908. 31 
(figs. 8 and 9). They arise from the side of the bracket on which a 
hydrotheca is placed, have no distinct stalk, and gradually increase in 
diameter upwards. At the summit they narrow again more suddenly, and 
terminate in a short but very evident cylindrical tube, the margin of which 
is exserted. The general shape of the profile of a gonangium varies from 
almost oval to obovate, and the walls in the upper two-thirds bear five or 
six distinct flowing ridges. The gonangia with male products are similar 
in shape to the female gonangia, but are slightly less in size and possess 
more marked ridges. Neither attain the diameter recorded by Vanhofien. 
The female examples are well developed, and each contains a narrow blasto- 
style and a large ellipsoidal gonophore which contains large ova from three 
to seven in number. (See fig. 9.) 
Dimensions . — 
Internode, length . 
diameter 
Hydrotheca, length adnate . 
„ free 
diameter . 
Gonangium, length 
greatest diameter 
. 0-52-0-89 mm. 
. 0-18 mm. 
. 0-08-0-10 mm. 
. 0-28-0-31 (0-38)* mm. 
. 010-0T3 mm. 
(male) 0’80-0'90 mm., (fern.) 0-97-0-03 mm. 
„ 0\31-0-46 mm., „ 0"44-0-45 mm. 
Localities. — Bay (east of Cape Royds), 7-8 fathoms, June 1908, rare, 
with male gonangia. M‘Murdo Sound, 25 fathoms, rare. Cape Royds 
(south), 10-25 fathoms, July 1908, common, with rare female gonangia ; 
20-30 fathoms, July 1908, rare, female gonangia ; 50-80 fathoms, 20th 
August 1908, common, with female gonangia. 
Distribution. — Sertularella plectilis is known only from Antarctic seas, 
from far-separated localities on the east side of the Antarctic continent : — 
M'Murdo “ Bay,” 20-130 fathoms (Hickson and Gravely) ; Gauss Station, 
385 metres (Vanhofien) ; and the recent records. 
Note on Sertularella plectilis, Hickson and Gravely, and Sertularella 
glacialis, Jaderholm. — Despite the similarity which exists between their 
gonangia, the only apparent difference here being that the gonangial 
aperture is borne on a longer neck in Sertularella glacialis, I cannot agree 
with Vanhofien in regarding these species as identical. The trophosomes, 
are sufficiently distinct. The colours of the two are different — in Sertula- 
rella glacialis, brown to very dark brown ; in Sertularella plectilis, pale 
straw colour to the pale transparent yellow of clover honey. This character 
* The figures within the bracket give length attained when reduplicated margins are 
included in the measurement. 
