1912-13.] Hydroicls of British Antarctic Expedition, 1908. 11 
GYMNOBLASTEA. 
Family Bougainvillim:. 
Atractylis antarcticus (Hickson and Gravely). 
Perigonimus sp., Hartlaub, 1904, p. 8, Taf. i. fig. 2. 
Perigonimus antarcticus , Hickson and Gravely, 1907, p. 4, pi. i. figs. 1, 2, 3, and 
pi. iv. fig. 32. 
Atractylis antarcticus , Vanhoffen, 1910, p. 283, fig. 8. 
For the most part very poor specimens, without gonosome and with the 
polyps obscured by adhering diatoms and other debris, indicate the presence 
of this species on the stems and branches of various larger hydroids. The 
occurrence of a few distinct polyps and of exceedingly scarce sporosacs, 
however, makes identification sure. 
The polyps observed are much contracted, and the hypostome is pro- 
duced to a point as sharp as that of a tentacle. The gonophores, all of 
which bear female products, differ from Hickson and Gravely ’s figure in 
possessing a considerably longer stalk, narrow at the base and widening 
gradually upwards until it merges in the base of the sporosac proper. The 
lower portion of the stalk is marked by indefinite annular wrinkles. In 
one case the upper portion of the stalk appears to form a cup, from the 
centre of which the sporosac arises ; but this is probably due to the 
destruction of an earlier sporosac, and the regeneration of a new one within 
the ruins of the old. 
The dimensions of our specimens are smaller than those of the specimens 
collected by the Discovery. 
I have followed Vanhoffen in attributing this species, on account of its 
sporosac reproduction, to Wright’s genus Atractylis. 
Dimensions . — 
Hydrocaulus, height 
diameter . 
Hydranth, length .... 
diameter .... 
Sporosac (female), length (excluding 
diameter 
length of stalk 
up to 5 mm. 
. H08-0T2 mm. 
. 023-028 mm. 
. 0T8 mm. 
stalk) H80-0 - 85 mm. 
. O50-O62 mm. 
. 0*40 mm. 
Localities. — M‘Murdo Sound, 25-50 fathoms, 6th July 1908, growing 
on Ophiodes arbor eus. Cape Boyds, 30-60 fathoms, 15th August 1908, 
on Ophiodes arbor eus ; 30-80 fathoms, August 1908, with sporosacs, on 
same host. 
