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. Now, let's take a look at the following section of the diagram. So in this section, we see that once we actually drill a hole in the zona palusa eventually that sperm cell will make its way to the membrane of that excel and the membrane of the sperm cell and the membrane of the xcel will begin to fuse. And as they begin to fuse, we have this opening where the nucleus of that sperm cell will make its way into the cytoplasm of that egg cell and eventually that sperm nucleus will make its way to the egg nucleus.