EFFECTS OF AGING UPON GERM CELLS. 



395 



Table VI. Continued. 



conditions. Then there occurred a period of rapid deterioration ,i.e.. 

 until the 4oth hour, and thirdly a long period of minimum cleavage 

 ranging from, ^oth to the yoth hour. Arbacia differs only in 

 the rate of deterioration, which is several times slower than in 

 Toxopneustes. 



4. The longevity of Arbacia eggs was correspondingly longer 

 than Toxopneustes, In experiment i, the eggs of 2 out of 4 

 females ceased to cleave when 48 hours old. In experiment 2, 

 the eggs of 4 females ceased to cleave at 42 hours ; the fifth female 

 at 65 hours, and the 6th female at 88 hours. In experiment 3, 

 cleavage occurred in all 3 females at least till the yoth hour, etc., 

 etc. The longevity ranged from 24 hours to beyond 72 hours, or 

 about twice that of Toxopneustes eggs, due largely to the difference 

 in temperature (about 10 C.) of the sea water. 



EFFECT OF AGE UPON SPERM. 

 Freshly Liberated Eggs Fertilized by Aging Sperm. Longevity of 



Sperm. 



In the reciprocal experiments, after the synchronously aging 

 germ cells, no longer cleaved, the aging sperm were tested against 

 freshly liberated eggs. 



