20 



MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



JoUos, though faint iudieations of it may be found in the cytoplasm beyond the 

 ends of the chromosomes in some of Borgert's figures (fig. D, 4). 



The next step in the process is the separation of the chromosomes into two 

 groups (fig. D, 4) and the formation of the new daughter nuclei (figs. D, 5, 6). 

 The chromosomes do not in this process lose their subparallel positions, but 



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S J.- 



'^^im^^ 









4 5 -^■.a-■-;:v-^^v;;; :.i:- 6 



Fig. D. Dirision of nucleus of Ceratiuin tripos var. svbsala forma t'jpica. After Borgert (1910, pi. 1, fig. 2; 

 pi. 2, figs. 11-1.5). 1. Resting stage of nucleus. 2. Prophase with nucleus shov\-ing a segmented spireme with 

 each thread double. 3. Equatorial plate stage. 4. Metaphase with division of the chromosomes. 5. Beginning 

 of the anaphase. 6. Later anaphase. X 800. 



this state seems to continue into the succeeding phases of nuclear development. 

 In the dividing nuclei of CoeJiloch'in'ion elomjntum (pi. 4, fig. 45) the same 

 appearance may be observed in the two newh" formed daughter nuclei. 



Jollos has figured for Gijrodinium fucorum, Ceratium tripos, and C. fasus 

 a " centrodesmose " connecting two granules which seems to have a very prob- 

 lematical relation to the mitotic figure. This, as well as other obscure points, 

 such as the exact method of division of the chromosomes and the iDresence of a 

 spindle, still requires further investigation before they can be definitely settled. 



The whole process of mitosis is of a relatively simple t.^-pe which, correlated 

 with the massive size and great number of chromosomes, makes it a distinctive 

 one in the Flagellata. The evidence for the continuity of chromosomes from 

 one division cycle to the next lies in the fact that the appearance of the daughter 

 nuclei in the late telophase stage (fig. D, 6 ; pi. 4, fig. 45) is snnilar to that jDre- 

 sented by the nuclei after final division of the body (fig. L, 2), and throughout 



