The museum snail that woke up after four years
In 1846 the British Museum received a desert SNAIL from Egypt, assumed it was dead, glued it to an identification card and put it in a display case. In March 1850 a curator noticed the card was discoloured. The snail was taken out, put in warm water, and came out of its SHELL to eat.
It had not been asleep in any ordinary sense. When conditions get too dry a snail seals the mouth of its shell with a chalky plug and shuts almost everything down, losing very little water and waiting. Desert species have been recorded doing it for several years at a stretch. The museum's specimen went on to live another two years, and its card is still in the collection with the dates written on it.
One slime, two completely different jobs
Snail MUCUS behaves in a way most materials cannot. Left alone it sets into a glue, which is how a SNAIL hangs upside down under a LEAF without falling off. Push it hard enough — the shove of a muscle wave running down the FOOT — and it turns abruptly runny, so the animal slides forward on a film of liquid.
Then it stops moving, and the slime grips again. The whole SLIMY business of gliding is that switching, thousands of times a minute, between stick and slip. It is also expensive: making the TRAIL costs a snail a serious share of its energy budget, which is part of why it is in no hurry. A garden snail covers about a metre an hour, and the silvery line left behind is the receipt.
Thousands of teeth on a tongue
A snail does not bite. It has a radula — a flexible strip that works like a conveyor belt of teeth, dragged over food to rasp fragments off it. A garden snail carries something in the region of fourteen thousand of them, in neat rows, and grows replacements from the back as the front ones wear away.
You can hear it if the house is quiet enough. A snail working at a lettuce makes a faint scraping sound, which is thousands of tiny teeth going over a leaf. Put one on a sheet of paper in the dark and the rasping is unmistakable — the least threatening horror-film noise ever recorded, and the reason gardeners find their seedlings reduced to stalks overnight.
Most slugs have a shell — on the inside
The obvious difference between the SNAIL and the SLUG turns out to be less obvious than it looks. Slugs did not simply fail to grow a shell; most of them still have one, reduced to a small flat plate buried under the skin of the shield behind the head. In a few species it is a scatter of chalky grains instead.
Losing the outside shell buys a slug the ability to squeeze through a gap the width of a coin and into the DAMP dark under a stone. It costs the protection, so a slug must stay wet and HIDE by day, coming out at night to MUNCH and to CRAWL across the SOIL. The rest of the grid is the working parts — the ANTENNAE and TENTACLE with EYES on the tips, the SPIRAL COIL of the shell, the SLOW GLISTEN of a trail across a garden path at dawn.