Imagine an assembly line for assembling things instead of
putting them together. Compare the earthworm's tubelike digestive system
to such a "disassembly line." What is the advantage of a tubelike
digestive system over a saclike digestive system?
When something reaches the end and there's something else behind it, what
happens in the two alternative cases?
Richard E. Barrans Jr., Ph.D.
PG Research Foundation, Darien, Illinois
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Update: June 2012