380 A. J. GOLDFARB. 



EFFECT OF AGE UPON MEMBRANE FORMATION. 



A third sympton of aging and physiologic deterioration is 

 the change in fertilization membrane. A number of inves- 

 tigators have observed that old eggs do not form fertilization 

 membranes (Hertwig, R. and O., '86, Loeb, '03, '15, Harvey, 

 '10, '14, F. R. Lillie, '14, etc.). Harvey ascertained the exact 

 age in Arbacia beyond which, namely 52 hours, no membranes 

 were formed. Just, '15, observed that the jelly layer, which 

 follows fertilization' in Nereis was retarded with aging. 



Before considering in detail the changes in the fertilization 

 membrane, with age, and the causes of such changes, it should 

 be recalled that freshly liberated eggs of freshly collected females, 

 when fertilized under constant and optimum conditions, varied 

 considerably in the rate of membrane formation. Such freshly 

 liberated eggs may be placed into three groups according to 

 their physiologic condition, namely (i) those that form mem- 

 branes within 2 minutes after fertilization, which are in good 

 physiologic condition. (2) Those that form membranes in 

 3 to 7 minutes, and which are in moderately poor condition, and 

 (3) those that do not form membranes, which are in poor physio- 

 logic condition. It should also be recalled that the rate of mem- 

 brane formation is further complicated by the differential effect 

 of eggs and sperm. I will mention but two of the experiments, 

 which are typical, to illustrate this differential effect. In experi- 

 ment I, Table II., the eggs of one female were fertilized by the sperm 

 of 5 different males. All the germ cells were 43 minutes old. 

 Four of the males induced membrane formation in I ^ minutes, 

 the fifth in 2 minutes. Even greater uniformity occurred when 

 the germ cells were I hour old, for the eggs of all 5 samples of the 

 same female formed their membranes at the same time, namely I 

 minute. When the germ cells were 1^2 an d 2 M hours old, the 

 eggs again reacted in the same manner for none formed mem- 

 branes. 



In contrast to this uniformity of behavior, when the eggs of one 

 female were fertilized by different males, are those experiments 

 in which the eggs of different females were fertilized by the one 

 male. For example, in experiment 2, the eggs of 3 females were 



