AGE, DEATH AND CONJUGATION 577 



period of higher diversified life is purchased at the price of ultimate 

 death. 



Minot has added to this fundamental idea certain views as to 

 quantitative relations of nuclear and cytoplasmic material in the cell. 

 Eelative increase of cytoplasm is taken to be the beginning of the proc- 

 ess of aging, while relative increase in nuclear material is considered a 

 process of rejuvenation. Such rejuvenation was held therefore to occur 

 in the early cleavage of the egg, since here the amount of nuclear ma- 

 terial was supposed to increase greatly in proportion to the amount of 

 cytoplasm. 



The recent important paper of Conklin has shown that in the cleav- 

 age of many animals this increase of nuclear material relative to the 

 cytoplasm does not occur. Conklin's results will apparently go far in 

 rendering untenable or modifying all theories in which great signifi- 

 cance is attached to the precise quantitative relations between nucleus 

 and cytoplasm. But what is important to realize is that this has no 

 bearing on the fundamental feature of the theory that aging and death 

 are due to differentiation. The grafting of the theory that the quanti- 

 tative relation between nuclear and cytoplasmic material is an essential 

 point upon this general theory was unfortunate from the beginning. 



Everything points, it appears to me, to the essential correctness of 

 the view which holds age and death to be the result of the greatly in- 

 creased differentiation of larger organisms. Is there then any proba- 

 bility that we shall some time find that in the higher animals, as in the 

 lower ones, death need not occur? 



Evidently not. If death is the price of differentiation, then after 

 the goods have been delivered the price must be paid. To prevent a 

 higher organism from undergoing death would at the same time pre- 

 vent him from becoming a higher organism. And the cell which re- 

 mains in the embryonic condition — the cell of the germ glands — is 

 even now as immortal as the cell of the infusorian. Death, as Minot 

 says, is the price we pay for our more complex life. Age and death, 

 though not inherent in life itself, are inherent in the differentiation 

 which makes life worth living. 



