EFFECTS OF AGING UPON GERM CELLS. 383 



i }4 an d i minute and none after 370 minutes. The average for 

 all 3 females at the give ages was 2.25, 2.05, 1.39, 1.25, 0.97 

 minutes, and none between 370 and 600 minutes when the experi- 

 ment terminated. A corresponding acceleration in the rate of 

 membrane formation, with age, occurred in all the other experi- 

 ments with physiologically good eggs. 



In the second group of physiologically poor eggs, there was also 

 an acceleration in rate of membrane formation with age, but sub- 

 sequent to this, there was a period of retardation, and ultimate 

 inability to form membranes. 



For example in Experiment 5, the eggs of 4 females were fer- 

 tilized by the same male when the germ cells were 75, 84 and 180 

 minutes old. The eggs of female no. I formed their membranes 

 at these ages in 2, I and 2 minutes respectively, in female 3, in 2^/2, 

 \^/2, and 4^2 minutes, in female 4 in 3^, 2 and 6 minutes re- 

 spectively. Female 2 alone did not show any retardation. The 

 average for all 4 females was 2.75, 1.62 and 3.62 minutes re- 

 spectively. 



In experiment 6, of the three females whose eggs showed an 

 initial acceleration, only one showed a secondary retardation. 

 The observations in this experiment were made at more inter- 

 mediate ages namely, 17, 42, 99, 161, 214, 294, 360, 420 and 430 

 minutes respectively. The eggs of female no. I formed mem- 

 branes in i ^, ij/2, ^/2, 1/3, -| minutes and formed no more mem- 

 branes after 420 minutes. The average rate for all three females 

 for the corresponding ages, was 1.22, 1.16, 0.66, 0.53, i.n and 

 1.83 minutes respectively, and none after 420 minutes. ' 



In experiment 7, 5 out of 6 females showed the initial ac- 

 celeration with age, and the secondary retardation. The average 

 for the 6 females for the following ages 130, 240, 350 and 470 

 minutes, was 2.08, 1.36, 1.83 and 2.08 minutes respectively. 



The results may be graphically represented as in Fig. i. 

 The ordinates represent the inverse time or rate of membrane 

 formation. The abcissas represent age of germ cells. With 

 physiologically good eggs, the time and rate of membrane for- 

 mation decreases with age, parts A and B of the curve. Beyond 

 certain limits when the eggs are in poor physiologic condition, 

 the time and rate is correspondingly increased, parts C, D, E, 



