HOST-PARASITE RELATIONS! INTESTINAL PROTOZOA 



nuclear membrane; one flagellum is much thicker than 

 the other. Longitudinal fission has been observed and 

 also stages that suggest multiple fission (Broughton- 

 Alcock and Thomson, 1922). The cysts of E. intestinalis 

 (Fig. lib) are pear-shaped and range from 4/1 to Qju in 

 length and from 2.5/x to 4.8/x in breadth. These stages 

 constitute all we know about the life-cycle of this species. 



6. TRICERCOMONAS INTESTINALIS (Fig. I2a) 



This species also lives in the large intestine of man but 

 has been recorded from less than 100 persons. It meas- 

 ures from 4fi to lOjU in length and from 3/x to 6/x in 

 breadth. The ovoid nucleus contains a large central kary- 

 osome. Two blepharoplasts are located on the nuclear 

 membrane. From the anterior blepharoplast three free 

 flagella arise, two of which are often fastened together ; 

 and from the posterior blepharoplast a single flagellum 

 arises, passes posteriorly through the cytoplasm and 

 emerges near the posterior end of the body. No cytostome 

 has been discovered. The cyst (Fig. 12b) is ovoid and 

 averages about yfi in length and 4. 5m in breadth. It 

 possesses two nuclei at one end, or four nuclei, two at 

 either end. Binary division occurs, but there is no evi- 

 dence of multiple fission. 



7. GIARDIA LAMBLIA (Fig. 13a) 



The optimum habitat of this species is in the duo- 

 denum. The trophozoite is bilaterally symmetrical. It 

 measures on the average, 13. 7m in length and G.Gfx in 

 breadth. The shape of the body in front view is indi- 

 cated in figure 13a. The ventral anterior portion is a 



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