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Definition: metamorphosis from Hawley's Condensed Chemical Dictionary

A process of developmental change whereby a larva reaches adulthood only after a drastic change in morphology; occurs in most amphibians and insects; for some insects, this change may include another stage (pupa) before the adult stage.

Summary Article: metamorphosis
from Philip's Encyclopedia

Change of form during the development of various organisms, such as the changing of a caterpillar into a moth, or a tadpole into a frog. Sometimes the change is gradual, as with a grasshopper, and is known as incomplete metamorphosis. Complete metamorphosis usually involves the more distinct stages of larva (such as a caterpillar), pupa (with a protective outer casing), and imago (winged adult).


When common frogs mate, fertilization and egg laying occur in water (1). Within an hour, the jelly around the egg swells to produce frogspawn (2). The eggs develop (3) and produce embryos (4) that hatch as long-tailed tadpoles with external feathery gills six days after fertilization (5). Mouths and eyes develop later and the tails become powerful means of propulsion. Hind legs are well formed by week eight (6); meanwhile, the tadpole has changed from a herbivore to a carnivore. Via an intermediary gill and lung stage, the tadpole changes from gill- to lung-breathing, its internal lungs growing as its external gills are absorbed; the process is complete when the gills fully disappear at month three, by which time the forelegs are well developed (7). Metamorphosis is complete when the young frog (8) loses its tail.

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