New observations on the structure of the hen ovum at ovulation

Scanning electron microscopy of the perivitelline layer (PL) of a hen body cavity ovum revealed dispersed groups of atrophied granulosa cells. Those overlying the animal pole were flattened and had numerous ramifying processes which penetrated the porous ground substance of the PL. Alternatively, the granulosa cells overlying the vegetal pole were rounded and formed fewer processes which penetrated a nonporous ground substance. The latter observation suggests that the PL is not structurally uniform in all ova.