PARASITIC WORMS— LEIPER AND ATKINSON. 



53 



are more uniform in size and shape The head is succeeded by a very short neck, and 

 segmentation begins almost at once. The segments are uniform nearly the whole way 

 down the body. The genital pores are single and unilateral. 



I had. The head is large. It expands from its narrow junction with the neck to 

 its bulbous end. It has four large suckers, which are deeply hollowed. They open 

 above on its upper surface, and run for some distance along its sides (text-fig. 10). 

 There is a free border formed by the nap making the edge of the sucker. The head 

 measures 0'92 mm. from side to side and I mm. from before backwards. It is roughly 

 square when looked at from in front. Kach sucker has an outside measurement of 

 0"44nim. and an inside measurement of 0':24 mm. 



Segments. -Unlike the last (Jestode. the uniformity of the shape and size of the 

 segments is marked. They measure 0'49mm. from before backwards, and ()"76mm. 

 from side to side. The borders are rounded, and they slightly overlap one another. 

 In a stained specimen the outer portion of the segments 

 remains unstained. The genital openings are unilateral and 

 occur at the sides, rather upon the ventral surface. The 

 opening measures 0'04 mm. and is rounded. The cirrus-sac 

 measures 0*14 mm. and is also rounded. The vagina is fairly 

 wide. The testes, which number •"><) to 40, are small and 

 rounded ; they are confined definitely to the space between t he 

 excretory canals on either side. They are also generally 

 arranged in three distinct sets — the number in the middle 

 set being far in excess of that in either of the other two. In 

 front of these and near the cephalic end of the segment are 

 the deeply-staining yolk-gland and ovary. The ovary is 0"06 mm. across and is 

 rounded. The uterus is a simple sac, and the eggs occur late in the hinder segments. 

 Two excretory canals run down either side, internally to the cirrus but externally to the 

 testes, and are continuous throughout the segments. 



The main differences from the previous Cestode are in the genital openings, the 

 number, distribution and arrangement of the testes, the shape of the head and suckers, 

 and the uniformity of the segments in shape and size. 



10. Tetrabothrius 

 aichesoni : view of the 

 anterior extremity of 

 the scolex. 



, 1914, p. 225. 

 Head 04 mm. in length. 



Testes 



:!5. Ti'trdhotlirius irrighti. Leip. and Atk. ( IT. I V, tig. 



Tetrabothvius wrigliti, Leiper and Atkinson, Proc. Zool. boc. 



Strobila 2*2 nun. long, none of the segments containing eggs, 

 constantly twelve. Auricular appendages of suckers well developed. 



//osf.- A few of these minute Cestodes were obtained from the gut of the Ade'lie 

 Pengun ( / h/goscelis <t<lt'H<tt>), a species which is usually peculiarly free from parasites of 

 any kind. 



Head.- The short neck is surmounted by a large head with tour suckers and 

 a peculiar rounded armature. There is no rostellum, nor do hooks occur. The head 



K L' 



