HOST-PARASITE RELATIONS I INTESTINAL PROTOZOA 



amy within the cyst as described in E. coli by Schaudinn 

 (1903), and in E. muris by Wenyon (1907) probably 

 does not occur. In fact Wenyon (1926) states that "it 

 is abundantly evident that no such autogamy process 

 occurs in the development of the cysts of any entamoeba." 

 Recent work also seems to disprove the observation of 

 Darling (191 3) that four uninucleate amoebulae are 

 formed within the cyst before hatching; of Yoshida 

 (1920) that the fusion of nuclei occurs after excystation 

 (in E. tetragena and E. coli) ; and of Mathis and Mercier 

 (191 7) that eight-nucleated cysts produce uninucleate 

 gametes that conjugate in pairs. Yorke and Adams have 

 shown by careful experiments that in culture the young 

 quadrinucleate amoeba usually either divides into two 

 binucleate animals and these subsequently into unincleate 

 forms, or uninucleate amoebulae separate one by one from 

 the quadrinucleate animal. Their cultures inoculated with 

 cysts gave for example at the end of 6.5 hours 19 per 

 cent of amoebae with 4 nuclei, i per cent with 3, and 5 

 per cent with 2, the rest of the original cysts being still 

 unhatched ; whereas at the end of 24 hours there were 3 

 per cent with 4 nuclei, i per cent with 3, 14 per cent with 

 2, 74 per cent with i, 6 per cent with many, and 2 per 

 cent still in the cyst stage. The detailed statistics show 

 a gradual change from quadrinucleate to uninucleate 

 forms. Multinucleate specimens were of frequent occur- 

 rence (up to 24 per cent) indicating that nuclear division 

 without cell division sometimes takes place in quadri- 

 nucleate amoebae after hatching. 



In what part of the digestive tract does excystation 

 take placed The data presented above dispose effectively 



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