EFFECTS OF AGING UPON GERM CELLS. 19 



Stout has reported similar results in Cichorium. 



King experimented with toad eggs and succeeded by drying 

 the eggs in materially changing the sex ratio. 



If it should be established that in these instances a change in 

 sex was really induced by the experimental condition, it could be 

 readily shown that in all these instances a physiologic deteriora- 

 tion of the eggs was the primary cause and affected profoundly 

 not merely the cytoplasm but the nuclear substance of the eggs 

 as well. It may be possible that aging modifies or destroys 

 the chromosomes in the same way that particles of the cytoplasm 

 are modified or destroyed. 



For, recent studies of Marine and Manley, of Patten, of Mac- 

 Nider and others point unmistakably to the conclusion that in 

 aging adult individuals there occur definite changes in different 

 tissues of the body, as well as in the blood stream, changes which 

 are profound in extent and correspond very closely to those I 

 have described in aging eggs. In view of these observations I 

 am led to believe that the reproductive tissues and the eggs of 

 older mothers would be correspondingly modified. And it is 

 also probable that the cyclical change in the aging eggs cor- 

 respond with and are caused by corresponding cyclical changes ire 

 the parental tissues. For it will be recalled that the eggs showed! 

 an initial period of increasing ripening, increasing fertilizability, 

 increasing rate of development, etc., until an optimum condition 

 was attained, and then there followed a long period of progressive 

 deterioration, modification and ultimate disintegration. 



Returning now to the consideration of the changes in aging 

 eggs, the question at once suggested itself. What then is the 

 fundamental nature of the physiologic deterioration, which 

 began with maturation and ended in the complete cytolysis of 

 the egg. The changes are twofold. There is, on the one hand, 

 a dissolving of the surrounding jelly layer, and, on the other hand, 

 a gelatinization and dissolution of the membrane-forming sab- 

 stances in the cortical layer of the egg. These twofold changes 

 are parallel. I find myself at variance with Harvey who held 

 that the loss of jelly under "normal" conditions was independent 

 of aging of the egg. My observations clearly show that if 

 proper precautions against mechanical shaking and changed HO 



