Giant paramecia

[TomMazanec]

Golden Age short story (but not too short). Man in LA area hears lecture about radiation causing mutations. So he gets himself some paramecia and exposes them to radiation. They grow to (iirc) large dog size. He tries to tell the scientific authorities. They all think he is a crackpot. Paramecia escape. He figures they will cause an ecological catastrophe and destroy civilization, so he flees to the mountains. Some months later he goes to a trading post and sees it filled with cans labeled with his giant paramecia. Vendor says they only can live in the LA area but they are the latest food sensation. "Guy who came up with them would be a millionaire if we knew who he was!" (and this was when a million dollars was a lot of money!)