152 SOME MINUTE ANIMAL PARASITES 



All pseudopodia are withdrawn (Fig. 31, A, B) and 

 food particles or excretory products are expelled from 

 the body. A thin membrane then appears at the sur- 

 face of the body and gradually increases in thickness. 

 Within the cyst wall thus produced, the nucleus 

 multiplies by a series of complicated divisions. Dur- 

 ing such division, some of the chromatin is absorbed, 

 and such temporary dissociation of part of the 

 chromatin and its subsequent reunion is considered 

 by some to represent a form of conjugation, and is 



c. 



FIG. 31 ENTAMCEBA COLI: CYST FORMATION 



A , Uninucleate form ; B, showing formation of eight nuclei j 

 C, cyst with eight well-defined nuclei 



termed autogamy. Eight nuclei are ultimately 

 produced (Fig. 31, C), and within the parent cyst 

 eight amcebulae form. If either the parent cyst or 

 the small daughter forms enter a new host with food 

 or drink, the cyst wall is dissolved, the amcebulae issue 

 forth, and infection ensues. 



Owing to the processes of binary fission, schizo- 

 gony, and cyst-formation of Entamceba coli there is a 

 great diversity of forms encountered in fasces con- 

 taining the parasite, and at any one stage the great 



