STUDIES OF AMITOSIS 507 



multiplication, especially in connection with rapid growth of 

 tissues. 



Third: Those derived from experimental works by Pfeffer 

 ('99), Nathanson ('00) and Wasielewski ('03, '04), demonstrat- 

 ing that amitosis can be induced by certain chemical changes in 

 external conditions, if the experimentally produced 'amitosis, is 

 identical with one occurring normally. 



Taking up the data of such nature as the first of these, I can 

 best cite from Hegner ('14), who concludes, after careful review 

 of the literature as follows: 



I have studied my preparations of chrysomelid beetles carefully 

 with the aim of detecting amitotic division and have observed what 

 appears to be direct nuclear division among the nurse cells, but could 

 not demonstrate with certainty this kind of division among the oogonia 

 or spermatogonia . . . . It is true that frequently dumb-bell 

 shaped nucleoli occur in certain of the nuclei and frequently two nu- 

 cleoli ar present at opposite ends. Also two nuclei may be surrounded 

 by a single cell-wall, but no stages were present which could not be 

 attributed as well or better to mitotic phenomena. 



From the evidence at present available, we must conclude that ami- 

 totic division of the germ cells has not been demonstrated, and that 

 not until such a process is actually observed in living cells will any other 

 conclusion be possible (p. 427-28). 



It is indeed inconceivable that such cells as have undergone 

 amitotic division may produce true ova or spermatozoa, unless 

 we assume an equal distribution of chromatin substance into the 

 daughter cells at the amitotic division. For such assumption, 

 however, we have at least at the present, no evidence at all! • 



Mitosis may of course follow amitosis in some cases, as actually 

 observed in the living condition by Mackhn ('16), but here the 

 daughter nuclei produced by amitosis do not divide by mitosis 

 themselves, but they fuse together, their chromatin substances 

 forming a single equatorial plate of chromosomes, and then the 

 division takes place in a normal way. Daughter nuclei in such 

 cases, are not independent nuclei, but they are really only parts 

 of a single nucleus as a reproductive unit. 



It may be that Meves and others observed phenomena similar 

 to that brought out by Macklin in living cells, but the study of 

 sectioned material did not enable the earlier authors to see the 



