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Webster 1913 Edition
Heteronereis
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Hetˊe-ro-ne-re′is
,Noun.
(Zool.)
A free-swimming, dimorphic, sexual form of certain species of Nereis.
☞ In this state the head and its appendages are changed in form, the eyes become very large; more or less of the parapodia are highly modified by the development of finlike lobes, and branchial lamellæ, and their setæ become longer and bladelike.