248 DR JOHN RENNIE AND MR ALEXANDER REID ON 



Dibothriocephalus wilsoni, Shipley. (PI. I. fig. 4.) 



This small tapeworm, which SHIPLEY (4) has already referred to as " very attractive " 

 in appearance, was also found by the Scotia 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 

 SHIPLEY'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. SHIPLEY'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 Scotia specimens are quite 10 mm. in length, 

 and have 1 8 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. (PI. II. 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 



(ROY. soc. EDIN. TRANS., VOL. XLVIII., 446.) 



