1 1 



" TERRA NOVA " EXPEDITION. 



segments are of a pearly white colour, varying to yellowish white at the hinder end. 

 Tin' segments, except those near the neck, show marked imbrication, and on the ventral 

 surface, at the hinder border of each, there is a marked V-shaped indentation. 



Head. — The head (text-fig. 8) is club-shaped, broadening near its apex and then 

 narrowing. It measures 1*35 mm. transversely, and 1mm. in a dorso- ventral 

 direction. The suckers are simple slit-like depressions which extend on to the summit 

 of the head, where they are separated by a fairly broad ridge. One lies on the dorsal, 

 the other on the ventral surface of the head. The lips of the suckers are narrow, with 

 the result that there is no folding. 



The lips approximate as they proceed down the head. The suckers have an 

 extreme breadth of 0 ' 58 mm. in front, and are 0 - 05mm. broad at the thin end. The 

 length from the front of the head to the end of the sucker is 1 mm. There is no 

 rostellum, and there are no hooks. The head tapers to join the neck, which extends 

 to about 0*7 cm., after which the first segments appear. 



Segments. — The segments are relatively wide, and vary in 

 breadth from 3 mm. near the head-end to 5 mm. near the tail. 

 They are exceedingly short, and markedly imbricated. 



The genital pores are in the middle line and are placed on 

 a slight projection. The surface of the segment is folded around 

 them to make a depression. The cirrus-sac is large, the cirrus itself 

 simple and unarmed, and measuring 0 • 3 mm. in length and 0 • 1 mm. 

 in breadth ; it is anterior to the vagina, which is a narrow straight 

 tube, 0'35 mm. long and 0'04mm. broad. 



The uterus is convoluted and occupies the central and lateral 

 portions of the segment. The testes are numerous and occupy the 

 imbricated portion of the segment as well as the central portion ; 

 some of them tend to be aggregated into small groups. Later the 

 segments become full of eggs at the expense of the other contents. 

 Well-marked bands of longitudinal muscular fibres are continued down the ventral 

 and dorsal aspects of the central portions of the segments. The circular fibres are not 

 so well marked. A single wide excretory canal runs down either side of the segment, 

 near its outer part. 



— Diphyllo- 

 boihrium perfo- 

 liatum, Railliet 

 and Henry : The 

 head, showing 

 the shallow lips 

 of the sucker. 



24. Dvphyllobotlvrium rufum, Leip. and Atk. 



DipJiyllobotJirium rufum., Leiper and Atkinson, Proc. Zool. Soc, 1914, p. 224. 



3 to 6 cm. in length. The head, which is characteristically pigmented brick-red around the base of 

 the suckers, measures 1-64 x 1*44 mm. The suckers are dorsal and ventral. The segments overlap 

 markedly, as in D. perfoliatum. The eggs measure O025 mm. 



Host. — WeddeU's Seal (Leptonychotes weddelli) ; small intestine, 



The worms are confined as a definite tuft to the first few valvulae conniventes as 



