EFFECTS OF AGING UPON GERM CELLS. 393 



were used. There was very little deterioration or dying until the 

 2Oth hour, and then a most rapid rate of destruction until the 

 24th hour, and a final residual minimum extending until the 

 48th hour. The eggs of female i died at 23 hours female 4 

 at 24 hours, female 3 at 25 hours, female 2 at 48 hours. 



Similar results were obtained in experiments 2, 3 and 4. Forty- 

 eight hours appeared to be the maximum longevity of the eggs of 

 Toxopneustes under the given experimental conditions. Table 

 V. gives the rate of deterioration of the eggs, Table III. of the 

 sperm. 



Arbacia. 



The experiments were repeated with Arbacia eggs, and the 

 inquiry was pushed further. The data are brought together in 

 Table VI. The facts may be summarized as follows: 



1. Eggs which no longer cleaved when fertilized by sperm of 

 the same age, did cleave when fertilized by freshly liberated 

 sperm. In experiment i, the increase was from o to 39 per 

 cent.; in experiment 2, from o to 56 per cent.; in experiment 3, 

 from o to 44 per cent., etc. This is exactly as in Toxopneustes. 



2. With further aging there occurred a second cycle of pro- 

 gressively decreasing cleavage. For example in experiment 5 

 24-hour eggs fertilized by i-hour sperm averaged for the 6 

 females 42 per cent. When the same germ cells were 31 and 8 

 hours respectively, they averaged only 10 per cent. A similar 

 secondary deterioration occurred in experiment I. The rapid 

 deterioration was due in both groups to the more rapid destruc- 

 tion of the sperm than of the eggs, as in Toxopneustes. 



3. The real deterioration of the eggs was determined as in 

 Toxopneustes by fertilizing aging eggs with freshly liberated 

 sperm at each testing. It was found that the eggs were very 

 long lived. In experiment 7, 2O-hour eggs showed little de- 

 terioration, 96 per cent, cleaved. Even when 41 hours, there 

 was little deterioration, for 81 per cent, cleaved. When 48 

 hours 19 per cent., when 65 hours 9 per cent., when 72 hours 

 I per cent. The other experiments, viz: 2, 3, 5, 6, 7, 8, 9, 10, 

 1 1, etc., gave similar results. They showed the same character- 

 istics as Toxopneustes eggs, namely, a long period of little deteriora- 

 tion, which in Arbacia is about 20 hour under the given experimental 



