Blackie, him that's Blindy now, and this other boy Willie Sawyer, and they were slugging and kneeing and gouging and biting and I see one of Blackie's eyes hanging down on his cheek.
The Dursleys often spoke about Harry like this, as though he wasn't there — or rather, as though he was something very nasty that couldn't understand them, like a slug.
What makes Elysia and a few closely related species in the Mediterranean and Pacific unique is how long they can hold onto chloroplasts — most other slugs keep them for a few weeks at most.