There is a difference between moving snails, earthworms, and slugs off the sidewalks, a difference in the feel of them between my fingers, and this difference is why I often, late at night, leave slugs in their silver trails on the sidewalks where otherwise I would relocate an earthworm or a snail.
I think that people tend to see that as a metaphor, tend to see that as something I say that I do to make a point, but I do it just as seriously as I do drop pennies, and as I did sink memories of Dream into South Lake Union. I think that people see gestures where I can't help but make actions, but I talk in metaphors a lot less often than some would imagine.
Earthworms are thin and stringy, even the largest of them, fragile, and though they could survive if cut in half they couldn't if half-ground into a sidewalk by an unthinking shoe, tethered to the crippled half of their bodies. Snails have a hard dry fragile shell perched on their back, which makes them easy to lift, but mostly I can't stand to think of the crunch a heel would make, crashing down on their house. Slugs, on the other hand are thick and sticky, and it is this I think that makes them a less sympathetic creature to look out for--because they feel between the fingers that they will break less easily than anything else.