94 PARASITIC AMOEBAE OF MAN. 



If one desires to study the changes occurring in 

 the nucleus during reproduction the best results are 

 obtained with special staining methods, and by the 

 use of a warm-stage or an incubator in which the 

 microscope can be placed during the examination. 

 It is possible to observe division of the nucleus in 

 the living parasite by the use of the warm-stage or 

 incubator, but patience is required in order to demon- 

 strate the changes which occur. 



The size of the nucleus varies, but it generally 

 measures from 5 to 8 microns in diameter. During 

 certain stages of division the nucleus may be either 

 larger or smaller than the average given, and during 

 this period it may be hard to distinguish. In most 

 instances the shape of the nucleus is spherical, but 

 sometimes it is distinctly oval in contour. It is 

 bounded by a well defined, heavy, nuclear membrane 

 which in the living organism appears highly refractile. 

 Upon the inner surface of this membrane there occur 

 brightly refractile elevations, generally hemispherical 

 in shape, consisting of nuclear chroma tin, and dots 

 and irregular granules of the same substance may be 

 observed scattered throughout the nucleus. At or 

 near the centre of the nucleus, during the vegetative 

 stage of existence, there are generally observed from 

 one to two very distinct masses of chromatin forming 

 the karyosome. The substance of the nucleus, aside 



