Evidence for the penetration of the vitelline membrane of the hen's ovum by a trypsin-like acrosomal enzyme.

In the process of fertilization, most mammalian spermatozoa must penetrate through a series of egg investments before reaching the vitelline membrane. By contrast, cock spermatozoa have only to penetrate the vitelline membrane of the hen's ovum. The composition of the vitelline membrane of the hen's ovum at the time of ovulation has been described by Bellairs, Harkness & Harkness (1963) as a single layer of connective tissue-like protein. Sperm penetration of the investments surrounding mammalian ova is aided by hydrolytic enzymes contained within the sperm acrosome. One of these enzymes is a trypsin-like enzyme (TLE) or protease which has been demonstrated by Stambaugh & Buckley (1969) to be active in the dissolution of the