140 SYDNEY J. niCKSON. 



process in the tissues of Vertebrates which does not lead to the 

 physiological multiplication and reproduction of cells^ but, on 

 the contrary, represents where it occurs a degeneration or 

 aberration, or perhaps, in many cases, is subservient to the 

 metabolism of the cell by increasing the periphery of the 

 nucleus/' 



Ziegler (65), who quotes the above passage from Flemming's 

 work, discusses in detail some of the many instances of 

 amitotic nuclear division, and comes to similar conclusions. 

 He says that amitotic division of the nucleus always indicates 

 the end of the series of divisions, and considers it hardly 

 probable that nuclei which have arisen by amitotic division 

 will ever again divide by mitosis. 



If Flemraing, Ziegler, and those who agree with them are 

 right, then it is clear that the oosperm nucleus does not and 

 cannot fragment. It must divide regularly by karyokinesis. 

 But Ziegler's views are, it seems to me, altogether unten- 

 able. By simply denying, or passing over in silence, many 

 instances of fragmentation of the nucleus, which do not 

 support his views, he has given undue weight to mitosis, and 

 leaves an unsatisfactory gap in the list of cases which support 

 his theory. 



Verson (56), Frenzel (12), and Lowit (40) have, since the 

 publication of Ziegler's paper, called attention to cases of 

 amitotic division of the nucleus which are most certainly not 

 followed either by nuclear degeneration or by a cessation of 

 cell multiplication. 



A review of the recent literature of cell division shows that 

 the cases given by these authors may be supplemented by many 

 others, and, indeed, leads one to a conclusion quite diflferent 

 from that of Ziegler and Flemming, namely, that indirect nuclear 

 division rarely occurs unless it is preceded by or accompanied 

 by some partial or complete segmentation or division of the 

 surrounding cell substance. 



It is undoubtedly true that in many cases amitotic frag- 

 mentation of the nucleus is followed by its degeneration and 

 the death of the cell. The numerous examples quoted by 



