Posted 4-3-00

There are lots of different things that people consider to be "worms." Actually, the term "worm" does not have a very precise zoological meaning.

Many zoologists would not even regard an earthworm as a type of worm. Regardless, there are probably about 10 or so major types of worms, or wormlike critters.

Two of the most abundant of these are the nematodes (or roundworms), shown at right, and trematodes (or flatworms). My understanding is that the term roundworm was coined over 400 years ago to distinguish nematodes from trematodes. There are several major anatomical differences... that separate nematodes from the trematodes. Body shape is not one of these. But nematodes are nearly always round, and trematodes are generally flattened. I hope this helps.

-- David Chitwood, research leader, USDA-ARS Nematology Laboratory, Beltsville, Md.

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