AMPHIMIXIS

 The membrane of the head and middle piece of sperm dissolves nucleus centrosome and mitochondria ,when it enters into the secondary oocytes .

Now the sperm nucleus enlarges to form pronucleus and egg those parts rotate through an angle of 180degre so that the mitochondria and proximal centriole of the associated middle place assume the leading position .

The initial path where the sperm penetrates the egg is called penetration path where the secondary path where male pronucleus fuse with female pronucleus is known as copulation path .

the mixing of male and female pronucleus to form zygote is called as AMPHIMIXIS or KARYOGAMY.

The mother is now said to be pregnant.