THE CESTODA OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 445 
Dibothriocephalus antarcticus. 
Bothriocephalus antarcticus, Baird, 1853. 
About a dozen or more examples of this species were obtained from the stomach of 
a Ross’s Seal, Ommatophoca rossi. These were all smaller than Barrn’s specimens, 
which were about 9 inches long. The Scotea examples range from 132 to 29 mm., 
but most measure about 100 mm. JBarrp’s (2) description is rather brief and confined 
to externals, but from this, together with his excellent figure, there is no mistaking the 
identity of the Scotza specimens with his type. 
This species was also found by the Discovery Expedition, and the specimens are 
described by Saiptey, to whose account reference is made below. 
Dibothriocephalus antarcticus, Baird (2), is a slender-bodied worm, with a conical 
scolex and with fairly sharp tapering point. The two suckers are long and compara- 
tively deep. According to Barrp, there are “two small rounded projecting lobes” at 
their posterior margins, but these in the Scotva examples are only occasionally present, 
and appear to be dependent upon the state of contraction of the animal. There is no 
neck ; the anterior part of the body for some distance behind the scolex is rounded, 
resembling an annelid in form; in the more posterior part the form is thick and 
flattened, being here elliptical in section. The colour is reddish yellow. The segments, 
even in the mature part of the animal, are very short; they are deeply constricted off 
from each other, and as the free margins are directed backward the segments appear to 
overlap more than they actually do. The only dimensions given by Barrp are : “ length, 
about nine inches; greatest breadth of body, about three lines,” and although the 
Scotia examples are very much smaller, the proportions agree well. The Discovery 
specimens come much nearer in length to the Scotia examples, although there is a very 
distinct discrepancy as regards width. SwipLey reports that most of the Discovery 
examples ‘‘ were just under 10 cm.,” and that “the greatest breadth is 7 mm. in the 
largest specimen.” ‘The longest Scotia worm is 13°2 cm., and its greatest breadth is 
4°5 mm.; most of the specimens are about 4 mm. in width. Again, as regards scolex 
dimensions, SHIPLEY gives “3 mm. in length and 3 mm. in breadth posteriorly.” In 
none of the Scotza specimens is the greatest breadth equal to the length of the head; 
they measure from 3 to 3°5 mm. long by 2 mm. wide. The actual differences here, 
however, are slight. 
A general account of the anatomy is given by Suiptey (4). He mentions that, 
besides the two longitudinal canals of the excretory system, “there are also small 
canals which lie close under the surface at the edges of the proglottides, usually two at 
each side, but they also break up from time to time into twisting branchlets.” These 
canals appear to be very numerous; from 42 to 45 may be present in a section, while 
at each lateral margin a group of four can usually be made out. 
The testes which occupy the central layer lie mostly towards the dorsal surface. 
There are from 18 to 20 follicles in a transverse section. 
