40 



'TERRA NOVA" EXPEDITION. 



The segments number from rive to six ; the broadest measuring 0'58 mm. transversely, 

 and 0'22 mm. from before backwards. None show genital glands. 



The genital pores are placed in the middle line, nearer the head-end of each 

 segment. 



The head is peculiar. It is relatively large, measuring 0 - 58 mm. in length, and 

 in its broadest part 0"34 mm. in width. On either side there is a large sucker, guarded 

 by peculiar lips, and having a small opening. The sucker is 0'39 mm. long, and 

 0"I8 mm. across in its broadest part. 



The worms are so immature that we are unable to give a specific diagnosis. We 

 place these forms, with some hesitation, under D. mobilis, Rennie and Reid. 



20. Dibothriocephalus coatsi, Rennie and Reid, 1912. (PL V, figs. 37, 38.) 



Host. — These small Cestodes were collected from the small intestine of Weddell's 

 Seal. They come from a slightly lower level than the preceding form. The infection 

 was in most cases an exceedingly heavy one, the whole of the inner surface of the 

 intestine being a felted mass of these minute worms. The intestine itself did not show 

 any macroscopic changes resulting from their presence. 



External < 1 haracters. — The worms are from 1 cm. to 1*5 cm. long, varying in colour 

 from dirty grey to brown. The head is narrow and is bluntly pointed at its apex. 

 There is only a very short neck, and the segments then become clearly defined at once. 

 These, with the exception of the first two, become elongated on passing backwards. 



Head. — The dorsal and ventral surfaces of the blunt, elongated head are grooved 

 by shallow, gaping slits or suckers, 075 mm. long ; these suckers do not extend on to 

 the top of the head. The head measures 1*1 mm. in length and 0"36 mm. across in its 

 broadest part, which is, roughly, just below the upper third. 



Segments. — The fourteenth segment (PI. V, fig. 38) is narrow above, widens in 

 front of the middle, and tapers again to the hind end. The segments do not overlap 

 each other in any way. In a stained specimen there is an outer, clear and unstained 

 portion at the periphery of the whole segment. The genital pores (c) are in the middle 

 line, much nearer the cephalic than the caudal end of the segment. The cloacal opening- 

 measures 01 mm. in its greatest length, and 0'06mm. in its greatest breadth. The 

 cirrus was not extruded in any segment, and therefore was not measured. The uterine 

 opening (</) is nearly circular, its diameter measuring 0'05 mm. in any direction. It is 

 placed immediately behind the cirrus-opening. The ovary, uterus (e) and female organs 

 are grouped for a short space behind this. The limits of the uterus are circumscribed 

 and do not extend far down the segment. This organ is simple and not branched, 

 and usually contains from eight to ten eggs, which first appear in the sixth to the 

 eighth segments, and measure 0'06 mm. in length. The testes number about ninety. 

 They are very distinct and are of a regularly rounded shape. They are not arranged 

 in any characteristic manner, but are scattered generally throughout the segments, 

 being fewest at the anterior border. 



