454 c - C - MACKLIN. 



which one portion only contains a skein, it is gathered that the 

 prophase in these cells is characterized by the spireme appearing 

 coincidently in the separate nuclear sacs (Fig. 25) ; later there is 

 formed from the double spireme a single equatorial plate of 

 chromosomes. Though these could not be counted there is no 

 reason for believing that their number was more than that normal 

 for the mononucleate cell. 



Not only has mitosis been demonstrated by observation, both 

 on living and fixed preparations, to occur in binucleate cells, but 

 it has been found that it occurs relatively as frequently in these 

 cells as in those with a unipartite nucleus. By making cell 

 counts in the aforementioned 20 preparations from chick heart 

 375 binucleate cells were found in a total cell count of 41,725. 

 Thus binucleate cells made up a percentage of the total of 0.9, 

 or a ratio of I in in. Among these binucleate cells 2 were 

 found which were in the prophase of mitosis, 1 a percentage of 

 0.53. Of the mononucleate cells, which numbered 41,106, 47 

 were in the prophase, or 0.114 per cent. By comparison of these 

 ratios it is found that mitosis occurs 4.65 times as frequently 

 among the binucleate as among the mononucleate cells; allowing 

 for the limited scope of the observation it seems reasonable to 

 conclude that mitosis is as frequent a phase of the life of binu- 

 cleate cells as of mononucleate, and it would seem that this is 

 their normal method of proliferation. If, in addition, they be 

 considered as dividing by direct fission (for which there is no 

 evidence either from living or fixed material) they would then 

 be possessed of an ability to multiply in excess of that of the 

 mononucleate cells, and there is no reason for supposing this to 

 be the case. 



No evidence was brought to light that the separate parts of 

 the bipartite or multipartite nucleus ever combine except during 

 mitosis. 



Another interesting observation was made in a fixed prepara- 

 tion, viz., that the early changes in the chromatin which presage 

 the onset of mitosis (i. e., the clumping of the chromatin and its 



1 Prophases alone were counted, in estimating cells in mitosis, since in this stage 

 alone is it possible to distinguish the bipartite from the moiiopartite nucleus, on 

 account of nuclear fusion in stages later than this in the case of mitosis in the 

 binucleate cell. 



