386 



DISCOVERY REPORTS 





14 



Figs. n-15. Tetrabothrius ruudi from Fin Whale. 11, scolex in lateral view; 12, cross-section of mature segment; 13, cross- 

 section through gravid segment showing uterus and uterine opening situated dorsally; 14, cross-section through portion of 

 longitudinal muscle; 15, egg. 



Tetrabothrius schaeferi sp.n. (Figs. 16-20). 



Tetrabothrius afflne. Baylis, 1926. 

 Tetrabothrius sp. Rees, 1953. 



Host: Blue Whale (Balaenoptera muscuhis). 

 Localities: South Georgia, Southern Ocean. 



The body is rather slender and flattened, varying from about 7 to 14 cm. in length and about 

 2 to 3 mm. in breadth. The segmentation is distinct. The scolex, provided with four suckers and 

 ' epaulettes ' is 3 mm. broad. A neck is present and well defined. 



The longitudinal muscles are seen to form two rings, if the segment is examined in cross-section. 

 The inner ring is composed of distinctly separated bundles, irregularly oval in outline and well 

 developed. Immediately, above the inner ring lies the external ring of longitudinal muscles which are 

 weakly developed, as are the circular and dorso-ventral muscles. 



The testes, about fifty in number, are about 90 x 90/x when measured in transverse section. They 

 occupy the dorsal part of the segment, being arranged in a single or many layers in fields extending 

 laterally and antero-posteriorly. The cirrus-sac, spherical or pear-shaped is about 30 n long and 150M 

 wide. The vas deferens is a much coiled, fairly well-developed organ. The well-developed ovary lies in 

 the ventral parenchyma. It is lobate and in transverse section more or less oval in outline. The egg- 

 cells are fairly large, about 21 /x in diameter. The vitelline gland is ventral to the ovary. The uterus is a 

 sac-like organ which as it matures gradually fills the medullary parenchyma. The uterine duct appears 

 fairly early in the strobila as a differentiation of parenchymatous tissue. The uterine opening is spherical 

 when observed in horizontal section. It is well marked, and surrounded with modified cells which 

 appear to absorb more haematoxylin than the counter-stain erythrosin. 



The egg is about 90 x 75 it in diameter, or more or less spherical. The inner membrane containing 



