Linked from
The 24 pages that link to Earthworm, each with the reason it gives.
Cutaneous respirationBroader topic: Earthworms depend on skin exchange rather than lungs or gills.
HermaphroditismBroader topic: Earthworms typically exchange sperm as simultaneous hermaphrodites.
AnnelidaBroader topic: Earthworms illustrate segmented locomotion and soil-based feeding.
ChaetaBroader topic: Its short chaetae grip soil as body segments extend and contract.
GizzardBroader topic: Its gizzard grinds swallowed material after it passes through the crop.