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Variation in Membrane Formation

females, eggs and rate

VARIATION IN MEMBRANE FORMATION.

In order to determine the normal variability in the rate of fertiliza tion-membrane formation, it was important to ascertain the degree of variability due to differences in different samples of sperm and that due to differences in different batches of eggs. A number of the experi ments to test this point are given in table 4.

When females Nos. 1, 2, and 3 in experiment 7/1 were fertilized by nude No. 1, fertilization membranes first appeared in 6, 4, and 4 minutes respectively. The same females tested at the same time by male No. 2 produced membranes in 31 minutes in one female, and none in the other two females. Male No.3 gave the same results as No. 2. In experiments 7/13 the membranes first appeared in 30 seconds to 3 minutes. With other males fertilized at the same time, eggs from the same females formed no membrane at all. Correspondingly wide variations occurred in the other experiments (6/9, 7/3, 7/2, 7/19).

Eggs that form membranes rapidly by one male may develop them slowly by another of the same age and apparently similar condition; but usually the rate of membrane formation is conditioned by the eggs. While the rate may vary with different males, yet each female tends to keep the same relative rate—i. e., there are slow-membrane-forming females and rapid-membrane-forming females.

In every experiment where different females were fertilized by the same male marked differences in the rate of membrane formation occurred. The correlation with cleavage on the one hand and jelly layers and size of the eggs on the other will be given later.

Since the rate of membrane formation varies with different males and with different females under the same experimental conditions, any comparison of results of one group of eggs with another must be made with great caution.