MORPHOLOGY AND BIOLOGY. 25 



each mass of chromatin being surrounded by a little 

 cytoplasm, thus forming a young amoeba. During 

 this process some of the chromatin is extruded from 

 the parasite while some remains as a residual mass or 

 masses. 



Reproduction Within a Cyst. When conditions 

 are unfavorable for the vegetative existence of amoebae 

 they undergo encystment and reproduction occurs 

 within the cysts. The method of reproduction within 

 a cyst varies in different species and occurs in two 

 different ways: either by the primitive mitosis of 

 the nucleus, followed by autogamous fertilization ; or 

 by the nuclear chromatin becoming dispersed through- 

 out the cytoplasm followed by the formation of 

 minute buds containing chromidia which are separated 

 from the parent body and form spores by the secre- 

 tion of a resisting membrane. In this condition they 

 are incapable of undergoing further development 

 until surrounded by conditions favorable to vegeta- 

 tive life. These methods of reproduction will be 

 considered more fully in the discussion of individual 

 amoeba?. 



Conjugation. It has been demonstrated that in 

 certain species of amoebae conjugation between two 

 individuals not infrequently occurs. I have observed 

 it repeatedly in Entamceba coli, and rarely in 

 Entamceba histolytica and Entamceba tetragena. 



