HOST-PARASITE RELATIONS I INTESTINAL PROTOZOA 



anterior flagella. Several investigators have reported 

 Enter omonas from man and Lynch (1922b) described 

 a species belonging to this genus in the guinea-pig. 

 Further evidence is necessary, however, before Enter- 

 omonas can be recognized with certainty as a separate 

 genus. 



5. GIARDIA 



The members of this genus (Fig. 13a) are bilaterally 

 symmetrical, have two nuclei, a ventral sucking disc and 

 four pairs of flagella. 



II. Specific Characteristics 



I. TRICHOMONAS VAGINALIS (Fig. "j) 



This is the type species of the genus Trichomonas 

 established by Donne in 1837. No cyst stage is known. 

 The trophozoite is comparatively large with an average 

 length of i6m and an average breadth of ii/x. The ante- 

 rior flagella are four in number and usually emerge from 

 the body in pairs, the members of each pair becoming 

 separate some distance from the body. They arise from 

 blepharoplastic granules situated near the anterior end of 

 the body. A fifth flagellum arises also from one of these 

 blepharoplastic granules ; it is fastened to the edge of the 

 short undulating membrane but does not extend beyond 

 the side of the body. A thin, chromatic basal rod lies 

 along the base of the undulating membrane. Spherical 

 chromatic granules lie on either side of this rod, often 

 arranged in a single row. The nucleus is large and spin- 

 dle-shaped, and contains many chromatic granules em- 



130 



