446 DR JOHN RENNIE AND MR ALEXANDER REID ON 
Dibothriocephalus wilson, Shipley. (Pl. L. fig. 4.) 
This small tapeworm, which Surpuey (4) has already referred to as “ very attractive” 
in appearance, was also found by the Scotva investigators, although not in the same 
host. These were obtained in the intestine of Weddell’s Seal along with numbers of 
Bothriocephalus mobilis, n. sp. The Discovery specimens occurred in Ross’s Seal 
(Ommatophoca rossi). 
It is a small, semi-translucent, delicate-looking Cestode, not undeserving of 
SHIPLeEy’s epithet. The scolex is short and conical in the contracted state, as appears 
in SHIPLEY’S figure. In more extended specimens, however, it is more rounded at the 
free end, as well as longer. An interesting point is the early appearance of mature 
segments ; the first of these may be but the fifth behind the head. Surpiey’s dimen- 
sions for this species are: length, 4 to 5°5 mm.; greatest breadth, 1 mm.; 9 to 13 
proglottides ; scolex,*5 mm. Some of the Scotva specimens are quite 10 mm. in length, 
and have 18 segments; one which measured less than 4 mm. contained 8 segments, 
none of which were mature, but in 5 of which the outline of the developing uterus and 
other sex ducts could be traced in a surface view. 
The only other point made out with regard to which SHIPLEY’s account may be 
supplemented refers to the dimensions of the ova. His figures are ‘042 by ‘035 mm., 
and these he gives as about the average. We find the ova do vary in size, and while 
we have not struck an average figure, we think that on the whole the dimensions we 
have to quote are fairly common and typical. These are ‘069 by ‘037 mm. 
The general appearance of this Cestode is given in fig. 4. 
Dibothriocephalus mobilis, n. sp. (Pl. I. figs. 7 to 10.) 
This is an extremely pretty little Cestode, highly translucent, which was found in 
the intestine of Weddell’s Seal, where it occurred in considerable numbers. It measures 
from 12 to 20 mm. in length, and is about 2 mm. at its widest part. The scolex is 
broad at its free end, narrowing towards its junction with the strobila. It measures 
‘5 mm. in diameter. The suckers are lateral in position, deep and widely gaping the 
whole length of the scolex, and having extremely mobile lips. They are capable of 
extension backward, showing in such a case large posteriorly directed flaps. Owing 
to the extreme mobility of the scolex, it is rather variable in form, although its general 
appearance remains characteristic (figs. 7 and 8). 
No neck is present. The segments are rectangular, at first narrow, being about 
twice as broad as long, lastly becoming practically square at the posterior end. The 
number varies from about 16 to 25; they are mature about the 7th or 8th segment. 
On a surface view the genital pores are seen to lie together close to the anterior border 
of the proglottis. 
The uterine pores are placed for the most part alternately right and left of the 
middle line in successive segments. The uterus in the immature segments shows three 
