Who demonstrated the acrosome reaction in Saccoglossus?

Which of the following methods is applicable in the case of a test tube baby?

After a sperm has penetrated an ovum in the process of fertilization,the entry of further sperms is prevented by:

$Statement I$: Penetration of sperm into ovum is a chemical process. $Statement II$: Acrosome of sperm secretes hyaluronidase which dissolves the corona radiata of the ovum.

Give scientific reasons: Enzymes are secreted from the cells of trophoblast.

Cleavage is followed by which stage?