18 University of California Puhlications in Zoology [Vol. 18 



Correlation op Mitosis with Cytoplasmic Structures and 



Changes 



That there are effects or changes possible in the cytoplasm which 

 can be correlated with mitotic activity taking place in the nucleus is 

 probably not doubted by any cytologist, but owing to the fact that this 

 problem of finding these cor-relations in the cells of Metazoa and Pro- 

 tozoa alike is wrapped up with biochemical and physiological com- 

 plexities, investigation in this field is attended with many difficulties. 

 In the Protozoa, although the biochemical and physiological conditions 

 are as complex as are those of metazoan cells, yet certain definite corre- 

 lations between mitosis and cytoplasmic structures and changes can 

 be the more readily detected because of the unusual development of 

 cytoplasmic organs in these lower organisms. 



The first change to be noted is the division of the blepharoplasts 

 and axostyle at the beginning of the prophase. This division of the 

 axostyle, as has been said in the discussion of mitosis, represents the 

 delayed division of this cytoplasmic organ following and belonging to 

 a previous mitosis. It is a cytoplasmic phenomenon which precedes 

 or initiates the next nuclear divisions, although it is completely 

 detached, except for the rhizoplast, from the centrosome. 



The phenomenon of polarity exhibited by the chromatin in its 

 arrangement during the prophase, as well as the direction of the major 

 axis of the spindle, is very significant in that for the most part it is 

 definitely related to the polarity of the body as a whole. Not only 

 was the single knotlike spireme nearly parallel to the major axis of the 

 nucleus, but also the two split spireme strands, and the major axes 

 of the chromosomes when they were completely formed. 



Very significant in importance is the seeming influence of the 

 centrosome. It was previously noted under mitosis that in the pro- 

 phase the distribution of the chromatin of the karyosome proceeded 

 along the axis or rhizoplast originating in the centrosome and extended 

 distally in this axis to the opposite pole to form the single axially 

 located spireme. Again, when this spireme split, the split proceeded 

 from a point in the chromatin nearest the centrosome posteriorly ; 

 likewise when the chromosomes were formed the first ones to be com- 

 pleted by segmentation of the spireme strands were located near the 

 centrosomes. The centrosome, even before its division, by the behavior 

 of the chromatin gave evidence of its potential influence over the 

 mitotic process. The entire number of eight chromosomes was, how- 



