NUCLEAR DIVISION WITHOUT CELL-DIVISION. I// 



layer) is increased, the electrical potential-difference of the sur- 

 face also alters in such a sense as to resist a continued increase of 

 surface, /. e., surface-tension is increased. The increase of sur- 

 face due to compression of the eggs --supposing the conditions 

 to be of the above kind must therefore heighten the normal 



o 



surface-tension ; it will consequently promote fusion. With re- 

 gard to the effects of withdrawal of water and raising of temper- 

 ature I have no suggestions to offer at present. Withdrawal of 

 water would result in a decrease in the number of dissociated 

 ions, but it is doubtful if the effect could be attributed to this 

 cause alone. 



IV. CONCLUDING REMARKS. 



On the view briefly sketched above mitosis is an incidental 

 consequence of the passage of the chromatin into the strongly 

 acid and chromatic phase ; this change involves the acquisition by 

 the chromatin of a negative charge of considerable potential, as 

 a result of whose inductive action there ensues a redistribution of 

 the ions in the cytoplasm with the production of certain differ- 

 ences of electrical potential. To these potential-differences are 

 due the appearance of the astral radiations and the diminution of 

 surface-tension that leads to cleavage. 



If this theory is well-founded it is evident that the ultimate 

 determining conditions of mitosis must be sought in the condi- 

 tions that control the chemical changes in the chromatin, espe- 

 cially those affecting the proportion of nucleic acid in this sub- 

 stance. In the mature egg the passage into the chromatic state 

 normally follows the introduction of a spermatozoon ; but the 

 same change may be artificially induced, as shown by J. Loeb 

 and his collaborators, by withdrawal of water, action of certain 

 electrolytes, or even by mechanical agitation. The change is of 

 a metabolic nature and as such is presumably dependent in large 

 part on the action of ferments. We may assume that the libera- 

 tion of the enzymes concerned, or their activity when liberated, 

 may be dependent on the presence of certain electrolytes. 

 Further speculation on this problem, however, seems premature 

 at present. 



Only the most general conditions of mitosis have been con- 

 sidered above. It is evident that, among other conditions, the 



