1910.] ESTT0Z0A OF THE HIPPOPOTAMUS. 243 



bifurcation of the gut. The genital atrium is small ; its wall is 

 formed by a thickening of the subcuticle. 



The testes, two in number, are large, smooth, spheroidal bodies 

 occupying the anterior third of the posterior half of the body, and 

 are situated diagonally one slightly behind the other. They measure 

 0-55 mm. antero-posteriorly, and 0-5 mm. dorso-ventrally, occupy- 

 ing practically the whole space between the dorsal and ventral 

 integuments. 



The vesicula seminalis is small and characterised by very few 

 coils. 



The pars musculosa is short, well defined, and provided with a 

 thick muscular coat. 



The pars prostatica has a greatly thickened wall composed 

 mainly of secretory cells. 



Text-fig. 31. 



|i ^ jf-£xp- 

 Paramphistomum bu.vifrons. Median longitudinal section. 



The ductus ejaculatorius measures O04 mm. in length, uniting 

 with the metraterm to form the ductus hermaphroclitieus and so 

 discharges into the slit-like atrium. 



The yolk-glands are poorly developed and lie wholly outside 

 the gut-branches ; the follicles are small and measure Ol mm. by 

 O05 mm. in diameter. 



The ovary lies between the testes and the excretory vesicle ; it 

 measures 0*25 mm. by 0*13 mm. 



The shell-glands lie lateral to and in contact with the ovary. 



The uterus has few coils. 



Laurer's canal passes outwards from the ovary to the dorsal 



16* 



