• nearly all snails are hermaphrodites
• because of this fact, snails can self-fertilize (!!)
• "some snails simultaneously swap sperm, while others will be male or female at a particular mating and then reverse their roles next time" (!!)
• some snails shoot calcium "love darts" into the other's body during the mating process; "it is thought that the dart transmits a slime containing pheremones that may improve the safe storage of the partner's sperm"
• some species make a new dart each time; others reuse them; some keep only one dart at a time; others have 2 or more in a "pouch"
• snails can keep their partner's sperm viable in them for months or years
• baby snails are born with their shells on, but the shells are soft
• the first thing a snail eats is the egg it hatched from, which contains lots of calcium to build its shell
• "if food sources are scarce, it may also eat a nearby unhatched egg or two that would otherwise have been a sibling"
• a snail shell grows concentrically outward, so older snails have more spirals in their shells
• most snails have a right-sided opening, but some are left-sided; "a snail must find a mate of its species with a matching shell"
• snails can mend their shells; "sometimes these animals are crushed seemingly to pieces, and, to all appearance, utterly destroyed; yet still they set themselves to work, and, in a few days, mend all their numerous breaches...but all the junctures are very easily seen, for they have a fresher colour than the rest; and the whole shell...resembles an old coat patched with new pieces"
• snails build a door (epiphragm) at the entrance of their shell using soil and leaves before the winter, in order to keep warm while hibernating. if it's really cold, they'll build several doors
• a snail's heart only beats 1-2 times a minute during hibernation
• snails can also go dormant during summer (estivation), for which they will construct a thinner epiphragm
• dormancy can last weeks, months, or years
• snails have over 2,400 teeth arranged in 80 rows (radula). the front rows fall out easily, so new teeth grow in from the back and all the rows shift forward
• they are apparently pretty loud eaters
• "some snail species are predatory, and a few are even cannibalistic and will bore a hole through another snail's shell or attack directly through an aperture. these snails have evolved fewer but longer teeth, which...they can fold out of the way to give more mouth room for ingesting their victims."
• snails breathe both through their skin and a breathing pore on the side of their head, the latter only opening about 4 times a minute
• snails have only one lung
• snails can survive dry periods by storing 1/12th of their weight in water in the mantle beneath their shell
• snails cannot hear
• they have 2 sets of tentacles: the upper used for smell and (very limited) sight, the lower for taste (salty, bitter, and sweet)
• injured tentacles can be regrown
• the tentacles are the only mucus-free part of a snail
• snails make different kinds of mucus for different purposes; "in a catastrophic accident in which a snail is squashed, it can release a flood of lifesaving, medicinal mucus packed with antioxidants and regenerative properties"
• the slime used for locomotion is called pedal mucus and it is incredibly sticky, allowing snails to travel upside-down and over a variety of surfaces, including (allegedly) the edge of a knife
• one experiment revealed that a snail could pull 9x its weight perpendicularly, 51x its weight across a flat surface, and 12x its weight suspended from its shell when upside-down
• "snails will often reuse their own or another snail's trail in order to save on slime production"
• "by detecting pheremones in a trail, they can determine whether it leads to foe, friend, or potential mate"
• "some terrestrial snails 'gallop' by picking up the front of their foot and leaping forward...if frightened, one species will lift itself up on its posterior and speed-glide 18 inches per minute"
• snails eat mostly dead matter and soil
• they are the only known land animal able to find calcium by smell
• they can absorb water directly through their skin
• "snails generally travel downwind from their daytime hiding places, then find their way home in the morning by following familiar smells"
• "many snails live out their lives in such close proximity to where they hatch that the botanist a.d. bradshaw once remarked, 'all i can say is, you've convinced me that this snail species is a plant'"
• they are nocturnal
• they lead solitary lives, except for when mating
• some species can live up to 25 years
• they like coming out after the rain
• microscopic snails exist (!!)
• snails have been able to colonize nearly every habitat on earth by hitching rides on larger creatures, including dinosaurs, birds, and insects (!)
• "stuck to an autumn leaf, a snail may blow along in a storm, its magic carpet eventually landing in faraway terrain"
• "it is even thought that microscopic snails may be swept up by the wind, rising on air currents until they join the fertile bank of animal and plant minutiae that inhabit the earth's atmosphere" (!!)
• snails have memory, are capable of learning, and can display fear. they also appear able to communicate with each other
• "confined snails may form an aggregate, their combined strength and skills leading to escape"
• snail defense mechanisms: shell retreat; slowness (avoids attracting attention of predators who look for quick movements); silent gliding (avoids predators who hunt by sound); mucus (can be too slippery for large predators to grab and smaller predators can get stuck or have their mouths gummed up); toxic mucus; camouflage; hiding

note: the majority of the info here and all of the quoted sections are drawn from elisabeth tova bailey's "the sound of a wild snail eating"