428 ANN BISHOP 



of the niicroiiucloi whilst still in their old position close to the 

 meganucleus. Their staining powers decreased as their size 

 increased. 



The increase in bulk of the chromatin sphere of the micro- 

 nucleus did not take place at the expense of the surrounding 

 halo, since this too increased in size and appeared as a wide, 

 clear area surrounding the swollen micronuclei (PI. 23, fig. 13). 

 It does not seem probable, therefore, that the increase in size 

 of the micronuclei was due to the absorption of fluid from the 

 surrounding halo, unless the latter obtains fresh liquid from the 

 surrounding cytoplasm. As they increase in size the micro- 

 nuclei move a little distance away from the meganuclei. 



In a large number of the animals studied a few of the micro- 

 nuclei, particularly those situated towards the posterior end 

 of the conjugant, appeared to be unaffected by this change, 

 and they retained their minute size. Such micronuclei were 

 often near to isolated fragments of meganucleus at the ]iosterior 

 end, even after the majority of the micronuclei were well 

 advanced in division. Their fate was not known, l)ut since they 

 were never present in the exconjugant immediately after 

 separation, one may presume that they were subsequently 

 absorbed. 



When the majority of the isolated segments of the mega- 

 nucleus migrated towards the anterior end of the conjugants 

 (see p. 425), the greater number of the swollen micronuclei 

 performed a similar migration and came to lie in the cytoplasm 

 between the scattered lobes of the meganucleus. A few^ of the 

 swollen micronuclei remained amongst the lobes of the mega- 

 nucleus at the posterior end of the body. These underwent 

 the same changes as did those at the anterior end. 



In their new position the micronuclei continued to swell. 

 Since the amount of chromatin did not increase, but was 

 merely distributed through a greater bulk, the micronuclei 

 became very pale and difficult to study. When they had 

 attained to their greatest size the swollen spheres began to 

 stain unevenly as though the chromatin was becoming aggre- 

 gated at certain points (PI. 23, fig. 12). It then became apparent 



