HYDROID ZOOPHYTES. 29 
annulated and very irregularly branched. They are not more than 0°1 mm. in 
diameter. 
The hydrothecse are elongated and everted at the margins. They are 
frequently reduplicated. 
The hydranths are 0°5 mm. in length and have about 20 tentacles 0°25 mm. 
in length. There are no nematophores in this species. 
Gonosome.—The gonothecse are oval (0°8 x 0°5 mm.) or spherical in both 
sexes. They are situated on short pedicels which may be irregularly annulated as 
in the British type. They are situated on the hydrocauli in no definite position. 
There is no evidence of any “coppinia’-lke grouping of the gonothece. 
The species Halecium tenellum was obtained by the ‘ Belgica’ expedition in 
70° S. by 91° W., and Bale mentions that he has one specimen in his collection 
from the Australian waters. It has also been found on the south Fuegian coasts 
and in Smyth Sound (10: pp. 505-509). It is common on the British and 
American coasts and extends into the Arctic seas (Jan Mayen). In fact, it appears 
to be cosmopolitan in Arctic and Temperate seas. 
SUB-FAMILY LAFOEINAE. 
LAFOEINA LONGITHECA. 
(Plate IV., fig. 31.) 
Lafoéina longitheca, Jéiderholm, Arch. Zool. Expér. (4), II. (1904), p. iv. 
Locality—McMurdo Bay, February 20th, 1902; 5-20 fms. 
Two small colonies of this hydroid were found creeping on the free hydrorhiza 
of Perigonimus antarcticus. 
Hydrosome.—A. well-developed hydrorhizal filament is attached to the support. 
From this there arise at intervals tall, cylindrical hydrothece (fig. 31) 0*7-1°0 mm. 
in height, slightly annulated at the base, and gracefully everted at the margin. 
The margin bears about twelve opercular flaps (fig. 31, op.), 0°11 mm. in length. 
Occasionally secondary hydrothece arise from the primary ones and attain an 
additional length of 0°25 mm. There is no distinct pedicel, the diameter of 
the hydrotheca at the base being almost as great as it is at the distal extremity. 
The hydranths are very small, being in the contracted condition not more than 
0:4 mm. in length, or about half that of the hydrotheca. A circlet of about eight 
tentacles surrounds the blunt conical hypostome. Each tentacle is about 0°15 mm. 
in length. 
Numerous upright nematophores, 0°12 mm. (but occasionally 0°2 mm.) in height 
by 0°02 mm. in diameter, arise independently from the hydrorhiza. They contain a 
delicate thread of tissue (fig. 31, d.), terminating in a pad at the extremity which 
is armed with a battery of nematocysts. 
Gonosome.—Not observed. 
