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Revision as of 21:55, 14 January 2002 by Clasqm (talk | contribs)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)Certain species of fish are ovoviparous. This means that while the fry still incubate inside eggs, these eggs are not expelled at an early stage of their development, but are retained within the female's body and the fry are allowed to hatch inside her befre they are expelled. These fish, for example the guppy, are among the most popular aquarium fish.
Placental mammals, on the other hand, are viviparous, and have dropped the egg stage altogether.