104 PARASITIC AMGEBJE OF MAN. 



the ectoplasm. At first this membrane appears single 

 in outline, but as reproduction proceeds a double out- 

 line develops and in some instances a well defined mam- 

 millation of the outer surface of the cyst wall occurs. 



The cytoplasm, after the formation of the cyst 

 wall, is perfectly hyaline in appearance and contains a 

 nucleus in which the chromatin appears to have 

 greatly increased in amount. If the cysts are placed 

 under conditions favorable to development reproduc- 

 tive changes occur in the nucleus which may be briefly 

 described as follows: 



The nucleus first divides by a primitive mitosis 

 into two daughter nuclei of the same size. These 

 two nuclei move to opposite sides of the cyst and the 

 cytoplasm gathers around them, dividing the organ- 

 ism into two partly separated portions. In the living 

 specimen the nuclei are observed to disappear after 

 several hours, but if stained specimens be studied it 

 will be noted that the chromatin of the nuclei is very 

 largely distributed to the cytoplasm, although a 

 definite portion of the nucleus remains, and from this 

 a new nucleus is formed. If living specimens be 

 watched it will be observed that after the disappear- 

 ance of the nuclei they will again reappear, but con- 

 tain much less chromatin and are of smaller size. 



Schaudinn describes certain variations in the 

 primary changes occurring in the nucleus as follows : 



