Abstract
1) The eggs undergoing the first maturation division are still surrounded by follicular epithelium. When such eggs are forced from the epithelium and inseminated in sea water or in an isotonic Ringer's solution, none of them is fertilized. The principal cause of the failure of fertilization is that the micropyle area of these eggs does not contain the sperm-activating factor which is an essential requirment for normal fertilization of the eggs.
2) Ovulation, i. e. liberation of the eggs from the follicular epithelium, takes place after the eggs have reached the second maturation division metaphase. The micropyle area of the ovulated eggs contains the sperm-activating factor. It has been found that when the recently ovulated eggs are inseminated in sea water or in an isotonic Ringers solution about 25 percent of them are activated and begin to cleave at the proper time. All of these eggs develop regularly (cf. Fig. 1 a-d). The remaining 75 per cent of the eggs, on the other hand, do not show any sign of activation in spite of the fact that they are penetrated by spermatozoa. These eggs remain unchanged for a number of hours. When such eggs are additionally stim-ulated by artificial means (pricking with a glass needle) all of them are activated at once and begin to develop (cf. Fig. 1 a'-d').
Some discussion was presented on this curious phenomenon on the basis of the “fertilization wave” concept proposed by T. YAMAMOTO ('44 a, b, '56, '58).
