1910.] 



ENTOZOA OF THE HIPPOPOTAMUS. 



239 



Gastrolhylax. The body measures 0*5 mm. to 0'8 mm. in length, 

 and is cylindrical in shape, tapering to a blunt point anteriorly, 

 the posterior end being truncate and occupied by the terminally 

 situated ventral sucker 0*9 mm. in dorso- ventral diameter, with a 

 muscular wall 1-8 mm. thick. All the specimens obtained were 

 sexually immature, but the peculiar configuration of the ventral 

 pouch is alone sufficient to distinguish this from all previously 

 described forms. The entrance to the cavity of this pouch is a 

 transverse slit on the ventral surface, 035 mm. from the oral 

 opening. "When seen in sagittal section the cavity has an almost 

 uniform breadth of 0*5 mm. from a short way behind the genital 

 pore to its blind end upon the dome of the ventral sucker. In 

 transverse section the cavity maintains a distinctly pentagonal 



Text-fig. 29 *. 



Gastrothylax cruciformis. 

 A, B. Transverse sections. C. Median longitudinal section. 



shape in all degrees of contraction of the body ; the ba.se of the 

 pentagon lying parallel to and upon the ventral surface, and the 

 apex projecting towards the dorsal surface of the parasite. In 

 certain conditions of contraction the two sides that form the 

 apical angle and the side that forms the base frequently buckle so 

 as to produce the figure of a cross ; tinder no circumstances are 

 the five angles obliterated. 



The cuticle is thin and smooth, with tiny knob-like papilke 

 near the mouth. 



The pharynx is small, globular, and measures 0"32 mm. in 

 length and 026 in breadth, the muscular wall being O09 mm. in 

 thickness. 



The oesophagus measures 0'2 mm. in length and O08 mm. in 

 breadth. 



* For explanation of abbreviations used in the text-figures see p. 251. 



