And what these enzymes do is it essentially reinforces that zonapalucida membrane. It changes the composition of zonapolucida and it forms the fertilization membrane. And this is shown in the following diagram. And what the fertilization membrane does is it prevents other sperm cells from actually entering that excel and so this prevents polyspermy from taking place. Now, this reaction that I just described, in which these cortical granules fuse with the membrane releasing these enzymes that change the composition of the zona pollucida and form the fertilization membrane is known as the cortical reaction. And it's the cortical reaction that prevents other sperm cells from actually entering that egg.