EFFECTS OF AGING UPON GERM CELLS. 405 



possessing the jelly layer, a decrease in rate of membrane forma- 

 tion, and a decrease in cleavage, varying in degree with the con- 

 dition of the eggs at the time of liberation. And one may predict 

 the extent of the other changes from any known one or two. If 

 size or membrane rate are known, one may predict very approxi- 

 mately the other symptoms of the physiologic condition of the 

 eggs, such as jelly and cleavage, etc. 



The discussion of these results will be postponed until further 

 data will be presented, concerning other types of changes in 

 very aged eggs. For the present I wish to draw attention to the 

 following considerations. 



1. The aging process or processes which are symptomized in 

 the various changes described in this paper begin not with the 

 liberation of the eggs, but upon their maturation, \\ithin the 

 body of the mother. This was first suggested by Loeb, and I am 

 in entire accord with his view. Hence it follows that chrono- 

 logic age (time since liberation) affords but a poor idea of the 

 real physiologic condition of the eggs either at liberation or at any 

 interval thereafter. 



2. Aging is a continuous process, beginning within the body 

 and continuing (with somewhat accelerated rate) outside of the 

 body, culminating ultimately in the death of the eggs. 



3. Aging was manifested in a number of ways, any one of 

 which may serve as an index of the physiologic condition, and the 

 degree of deterioration. The ensemble of the various indices 

 forms a clear and unmistakeable measure of their condition and their 

 deterioration. 



4. While no attempt has thus far been made to describe the 

 nature of the chemico-physical processes involved in the aging 

 of the eggs, they may nevertheless be accurately measured. 

 It is now possible to measure very accurately the physiologic con- 

 dition of the eggs at liberation, and at any interval of time there- 

 after, to measure accurately the rate of deterioration or sene- 

 scence under given experimental conditions. It is also possible 

 to measure the real longevity of the eggs or of the sperm. 



5. These data, and those described in Part III., afford a basis 

 for an understanding of the nature of the aging process, and of 

 the means of controlling senescence of the germ cells. 



