I know these questions have probably been asked before…but I’ll fire away anyway… 
Firstly - If you cut a garden worm in half (not that im suggesting you should do this), do both the ends live, or just one?
Secondly - Do worms ‘mate’ or are they an asexual reproductive organism thingy?
IIRC Earthworms are hermaphrodites; they mate, becoming joined by a blob of mucus into which (I think) they both deposit eggs and sperm, they wriggle out of the blob and it toughens to become a protective casing for the eggs. (That’s what I recall from school, anyway).
Oki, chrz for that :)…now how about the chopping in half bit?
How difficult is it to chop the wriggly critters in half anyway? They never seem to cooperate by lying still while you do the deed. Howevah on numerous sunny afernoons I’ve cut worms in half while fishing, both ends seem to live but sadly death follows from drowning (rarely from a fish biting, sadly).
Yeah, I know that both ends wriggle (was’nt me that did the nasty deed ;))…but is it the case that they both go on and ‘live’, or is it just the ‘cutting a head of a chicken and the body runs about a bit’ situation?
Carnage. :o
The “band” (clitellum) you see on an earthworm is the “naughty bits”. Some amplification on Mangetout’s explanation:
http://members.aol.com/camusurca/earthworms/reproduc.htm
Since the creature DOES have a mouth end and an anus end (not readily apparent to casual observation, I will admit), and differentiated systems like digestive / circulatory systems that extend the length of the worm, I would guess that both halves die. The heart and the brain (yes, an earthworm actually has a brain) are at the front end.