392 JULIA ELEANOR MOODY 



cannot be traced to a disturbed relation between nucleus and 

 protoplasm. These varying ratios found in cells of the same 

 period in the life history of the organism, may be explained 

 on the basis of differences in cell metabolism. Cultures sub- 

 jected to comparatively constant environment showed wide 

 individual differences in response to artificial stimulation and 

 it seems probable that the variations in the kernplasma-relation 

 are individual variations due to a difference in response to en- 

 vironmental conditions, since the interchange of nucleus and 

 protoplasmic material is dependent upon the metabolic activity 

 of the cell. Conklin states in his paper on ''Cell size and nuclear 

 size" that ''As we have seen, the kernplasma-relation varies 

 widely in different blastomeres of Crepidula and Fulgur. In 

 these cases wide departures from the kernspasma-norm have 

 not brought on cell division and if the kernspannung is a cause 

 of cell-division, it must be a minor factor in the case." From 

 the evidence at hand therefore it seems impossible to trace 

 the phenomena of cell division to any of the causes thus far 

 suggested by Spencer, Strasburger, Boveri or Hertwig. Cell- 

 division is the index of protoplasmic vitality which is directly 

 dependent upon the metabohc activity of the cell. If therefore, 

 we accept Child's interpretation of senescence and rejuvenes- 

 ence, we must attribute the varying relations between nucleus 

 and protoplasm to individual differences in metabolic activity 

 expressed in the division-rate. 



Strasburger ('93-) accounts for cell division on the basis of 

 the 'working-sphere' of the nucleus. The experimental work 

 of Brandt ('77), Nussbaum ('84), Gruber ('85), Lillie ('96), 

 Balbiani ('89 and '91) and Verworn ('89) all go to show that 

 the nucleus is indispensable to the formative energy of the cell; 

 that although the processes of destructive metabolism may 

 continue for a long time in an enucleated cell, that constructive 

 metabolism is only possible in the presence of the nucleus 



Considering these facts in connection with Strasburger's theory 

 of the 'working-sphere' of the nucleus, the ratio existing between 

 the nuclear surface and the protoplasmic mass must be of great 

 significance in the interchange of nuclear and protoplasmic 



