Hawaii's native tree snails, known as the "jewels of the forest," are rapidly disappearing. Some of the most imperiled only live in human care now, safeguarded 24 hours a day.

NPR's Ailsa Chang speaks to slime scientist Antonio Cerullo at the City University of New York about the benefits of mucus.

Even a snail, the movie eventually reminds us, can only move forward. Memoir of a Snail Rated R for clay nudity, violence and alcoholism, as well as talk of adult matters.