EFFECTS OF AGING UPON GERM CELLS. 409 



The real longevity of the eggs depended upon the physiologic 

 condition at time of liberation, the better, the longer lived, and 

 vice versa. 



The rate of cleavage was accelerated for a time and then re- 

 tarded with age, more so in physiologically poor eggs, less in 

 good eggs. 



When ageing sperm fertilized freshly liberated eggs the 

 decrease in cleavage was surprisingly small. Very little decrease 

 occurred when sperm were 73 hours, only a little more when 

 sperm were 95 hours old. 



The explanation for the greater longevity of the sperm is 

 found in the fact that the sperm aged in the "dry" condition, in 

 which they are inactive and hence minimum metabolism. 



The greater decrease in cleavage in synchronously ageing germ 

 cells is due to a summation of the injurious effects upon the sperm 

 and upon the eggs. 



In very late stages in ageing of sperm, the reduction may be 

 due not so much to physiologic deterioration as to insufficient 

 numbers of sperm. There is ground for belief that no matter 

 how old or deteriorated the sperm if they are active (alive) they 

 can penetrate the egg. It is not so clear whether such aged sperm 

 cause parthenogenesis or sexual development. 



The change in size, jelly, membrane and cleavage with aging 

 of germ cells, are accurate, convenient and corroborative indices 

 of chemico-physical and morphologic changes in the egg as they 

 age, and afford convenient measures of the loss in vitality, or 

 physical deterioration. And one change may serve for this pur- 

 pose. Their ensemble is convincing. 



In the next study will be considered the changes in much older 

 germ cells leading towards their cytolysis and death. 



