TheBioCosmos on Instagram: "Here is the explanation to my previous amphibian embryo rotating video. The phenomenon is called cortical reaction. It's important to note that this is NOT cortical rotation, which is a different phenomenon happens AFTER cortical reaction. The swelling of the vitelline membrane is purely due to osmosis and this prevents polyspermy, while the darker pigmented part (which is called the animal pole is less dense than the vegetal pole - the lighter coloured part, because