406 Philippine Journal of Science 19 1» 



As a rule, in dividing cells of the Ciliata, the micro-nuclei 

 divide first by mitosis, division of the meganucleus which comes 

 later being of a direct type often, apparently, in the nature of 

 a more or less mechanical partition of the chromatin. 



In the case of Boveria subcylindrica, a more or less aberrant 

 genus but with close affinities to the Heterotrichida, as described 

 by Stevens (11), the relation between the meganucleus and the 

 micronucleus at division of the former is much more intimate. 

 At division the micronucleus comes to lie in contact with the 

 meganuclear membrane. The spindle appears usually at one 

 side, but near the posterior end of the meganucleus. Later it 

 stretches along the nuclear membrane with its poles approaching 

 the ends of the meganucleus. The two micronuclei when sepa- 

 rated are located at or very near the poles of the dividing mega- 

 nucleus. It would seem clearly indicated from this that the 

 micronucleus wields a distinct influence over division of the 

 meganucleus, a much more direct influence than is shown in 

 Ciliates generally. 



Ikeda and Ozaki(G) have recently described another interest- 

 ing relation between the mega- and micronuclei of Boveria 

 labialis, a new species occurring in the respiratory trees of two 

 Japanese holothurians. Unfortunately, I have been unable to 

 obtain the original paper and have only seen it in abstract. The 

 phenomenon was observed in conjugation. Following zygosis, 

 the synkaryon divides twice. One of these daughter nuclei 

 becomes the micronucleus of the reorganized individual. The 

 other three products of this division undergo degenerative 

 changes and become incorporated into the persisting meganu- 

 cleus and may be traced in the first and second fissions of the 

 exconjugant boverias. 



This merely gives a possible clue to what is going on in this 

 species of Balantidium. It seems possible, and indeed is sug- 

 gested by some of the figures, that the micronucleus in its in- 

 corporation into the meganucleus may come to function as a 

 division center within the substance of the meganucleus, sep- 

 arating out and resuming its identity at the conclusion of the 

 process. In a way this would merely constitute a variation 

 in the process described by Miss Stevens. As to my observation 

 that this constitutes a post-conjugation phenomenon, that must 

 be laid aside, for the present, for the reason that no earlier 

 stages of conjugation have been seen. 



Several other interesting cytological points in this species need 

 clearing up, but they must be left for future work. 



