1. 26-3 Cnidarians

2. Cnidocyte
• Stinging cell of cnidarians; used for defense
and to capture prey

3. Nematocyst
• Stinging structure within each cnidocyte of a
cnidarian that is used to poison or kill prey

4. Polyp
• Usually sessile stage of the life cycle of a
cnidarian that has a cylindrical body with
armlike tentacles

5. Medusa
• Motile stage of the life cycle of a cnidarian
that has a bell-shaped body.

6. Gastrovascular Cavity
• Digestive chamber with a single opening, in
which cnidarians, flatworms, and echinoderms
digest food

7. Nerve Net
• Loosely organized network of nerve cells that
together allow cnidarians to detect stimuli.

8. Hydrostatic skeleton
• Layers of circular and longitudinal
muscles, together with the water in the
gatrovascular cavity, that enable movement

9. External fertilization
• Process in which eggs are fertilized outside the
female’s body

10. Key Concept
• Cnidarians are soft- bodies, carnivorous
animals that have stinging tentacles arranged
in circles around their mouths. They are the
simplest animals to have body symmetry and
specialized tissues.

11. Key Concept
• Cnidarians typically have a life cycle that
includes two different- looking stages: a polyp
and a medusa.

12. Key Concept
• Cnidarians include jellyfishes, hydras and their
relatives, and sea anemones and corals