HOST-PARASITE RELATIONS: INTESTINAL PROTOZOA 



20ju. The nuclei are 8 in number in the mature cyst, but 

 cysts with i, 2 and 4 are commonly found and more 

 rarely with 16 or more. Glycogen occurs in early stages 

 in greater amount than in cysts of E. histolytica; it is 

 rare in 8-nucleated cysts. Chromatoid bodies are often 

 present especially in early stages; they may resemble 

 splintered glass or be filamentous. 



Life-cycle. This species has been found only in the 

 large intestine of man and about 50 per cent of the 

 general population is infected. The stages described above 

 are the only ones known with certainty to occur. The 

 trophozoite undergoes binary division during which the 

 nucleus probably divides by mitosis. The cysts are sup- 

 posed to give rise to 8 amoebulse on hatching. Nuclear 

 division within the cyst has been described by Swezy 

 (1922) as mitotic involving the formation of probably 

 six chromosomes. 



3. ENDAMCEBA GINGIVALIS 



Trophozoite. The trophozoites of E. gingivalis (Fig. 

 5) range from 6m to 60ju in diameter but are rarely over 

 20ju. The clear ectoplasm is distinct from the granular 

 endoplasm and locomotion is fairly active. Kofoid and 

 Swezy (1924c) describe a distinct pellicle. The nucleus is 

 of the endamoeba type, smaller than that of E. coli, and 

 with a karyosome either centrally located or eccentric. 

 The food vacuoles contain bacteria, leucocytes, etc. ; red 

 cells have rarely been reported in them. 



Life-cycle. So far as we know the life-cycle of this 

 species contains only the trophozoite stage. The mouth 

 is the normal habitat and although exact figures are not 



62 



