557 



made by various authors that araitosis accompanies intense nuclear 

 activity of some kind and the belief that it results in degeneration is 

 held by many. 



While the case of Moniezia seems to indicate the existence of a 

 relation between nuclear activity and amitosis, I am inclined to believe 

 that a relation between amitosis and degeneration exists only in so 

 far as in regions or periods of intense nuclear activity many nuclei, 

 in some cases perhaps all, are likely to degenerate. The nuclear de- 

 generation in the testes of Moniezia is probably a case in point. The 

 activity resulting in degeneration is doubtless due to some intense 

 stimulus affecting the nuclei and bringing about chemical or physical 

 changes with such rapidity that all reserves are exhausted. If this 

 condition is not reached the nucleus may recover and continue its 

 existence. Just what the conditions may be which lead to fragmen- 

 tation of the nucleus, i. e. amitosis, we cannot determine at present. 



It appears probable, on the other hand, that if fragmentation does 

 not take place in growing cells, gradual changes occur in consequence 

 of which mitosis occurs sooner or later. In this case the cell passes 

 through a certain series of changes which culminate in mitosis. Where 

 amitosis occurs the conditions which result in fragmentation do not 

 permit the completion of this series of changes. In short, the celj 

 dividing mitotically is in a condition differing physiologically from that 

 in which amitosis occurs. Probably the different methods of division 

 correspond to different complexes of metabolic processes. More than 

 this present knowledge does not permit us to say. 



I am inclined to believe that the occurrence of isolated mitoses 

 in the early stages of testes and ovaries and in the parenchyma of 

 Moniezia indicates simply that these nuclei are less affected by con- 

 ditions of a particular kind. The gradual increase in the frequency of 

 mitosis probably indicates a gradual decrease in the intensity of these 

 conditions or a change in their character. 



But my observations also bear upon problems of a more general 

 nature. If cells which pass through a long history of amitotic division 

 are capable of giving rise to sexual cells it is difficult to see how the 

 hypothesis of the individuality of the chromosomes can be maintained. 

 Defenders of this hypothesis may claim that all the chromatic sub- 

 stance is concentrated in the nucleolus, that there is in this a definite 

 region or "sphere of influence" corresponding to each chromosome, and 

 finally that each new nucleolus arises from the old, each receiving an 

 equal part of each of the regions. All that can be said against a 

 hypothesis of this sort is that there are no facts to support it. It 



