The clown is able to adapt itself chemically to mask it's presence.
Steve, I don't know if this is scientifically proven. There are so many several hypothesises (sp?) out there regarding the issue of how a clownfish protects itself.
1) Hypothesis of camouflage: clownfish smear themselves with anemone mucus and is not recognized by the anemone.
2) Hypothesis of inert mucus: clownfish mucus is an inert substance that fails to evoke nematocyst discharges.
3) Hypothesis of thick mucus: clownfish mucus thickens upon entering an anemone and the thick mucus prevents it from being stung
4) Hypothesis of customized mucus chemistry: clownfish decrease the synthesis of substances within its mucus that excite nematocysts
5) Hypothesis of innate protection: juvenile clowns are not stung when they enter an anemone because the tentacles cannot adhere to them
No doubt, clownfish posess some amazing characteristics that enable them to survive within the stinging tentacles of anemones and some scientists believe that how clownfish do this varies from species to species.