. 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 (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 segmen
. 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 (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 30n 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 modifie
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