What are cnidocytes? What is the name of the capsule inside the cnidocyte? What are the biological functions of this structure?

Cnidocytes are specialized cells present in coelenterates. They are found in the epidermis and have toxic substances that can hurt, paralyze or even kill other animals.

Every cnidocyte has an internal capsule know as nematocyst where the actual urticating substance is stored. When a cnidocyte is excited it causes the nematocyst to expose a filament having the toxic chemical.

Cnidocytes and their nematocysts have the biological functions of defending the individual from external aggression and of helping to capture their prey.