248 DR. R. X. LEIPER on [Feb. 1, 



level of the posterior edge of the second testis ; it does not cross 

 the excretory vesicle in any part of its course. 



The excretory vesicle as seen in longitudinal section is Y-shaped, 

 embracing the shell-glands within its two arms ; its cavity merges 

 almost insensibly into the short excretory duct which passes back- 

 wards to open at the level of the dome of the ventral sucker 

 1*2 mm. behind Laurer's canal. 



The above measurements are all taken from serial sections of a 

 single specimen 6 mm. in median longitudinal section. 



10. Paramphistomum pisum, sp. n. (Text-fig. 34.) 



This form, unlike those hitherto described, lives in the small 

 intestine. It is white in colour with the faintest tinge of pink. 

 In shape it is pisiform, but the specimens preserved all exhibit a 

 certain amount of contraction. The ventral sucker lies sub- 

 terminally, and its aperture as seen with the naked eye is a minute 

 pore no larger than that of the mouth (0*3 mm.). Its greatest 

 diameter is 1'7 mm. ; the muscular wall is 0*4 mm. thick, the 

 cavity l'O mm. wide. 



The dorsal cuticle is 0*02 mm. thick and is differentiated into 

 two parts, the external layer being 0*01 mm. thick, and there do 

 not appear to be any papillae at the anterior end of the body. The 

 cuticle on the ventral surface is very thin. 



The pharynx lies some distance (0'9 mm.) from the oral pore, 

 is globular in shape, 1*2 mm. long, 1"1 mm. broad, and its muscular 

 wall is 0"4 mm. thick. There are no pharyngeal pouches. 



The oesophagus is short, exceedingly wide, and in contracted 

 specimens shows several transverse folds. Its wall has thick 

 strands of muscle. It measures 03 mm. in length by 0*6 mm. in 

 breadth. 



The gut-branches are also very wide, measuring 0*6 mm. 

 The genital pore lies only - 9 mm. behind the oral opening 

 (and in contracted specimens) at the level of the centre of the 

 pharynx. 



The genital atrium is small and fissure-like, and its wall is 

 composed of an inward extension of the sub-cuticle, which is 

 sharply marked off from the parenchym. A few muscular fibres 

 are seen in its wall. 



The testes are large and deeply lobed : they lie in the ventral 

 half of the body, and occupy almost the whole of that region 

 between the pharynx and the ventral sucker. It is impossible 

 from serial sections to ascertain exactly their individual size ; they 

 appear to lie one in front of the other. 



The vesicula seminalis is a thin-walled voluminous tube 

 crowded with sperm-cells. It completely fills the ventral half of 

 the area intervening between the bifurcation of the gut and the 

 anterior testis. 



The pars musculosa is spirally coiled and there is a fair amount 

 of contractile tissue in its wall. 



