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Very imperfectly developed; in an early stage of development; embryonic.

or pertaining to the segmental organs. Segmental duct (Anat.), the primitive duct of the embryonic excretory organs which gives rise to the Wolffian duct and ureter; the pronephric duct. -- Segmental organs. (a) (Anat.) The embryonic excretory organs of vertebrates, consisting primarily of the segmental tubes and seg…

-- Shell gland. (Zoöl.) (a) A glandular organ in which the rudimentary shell is formed in embryonic mollusks. (b) A glandular organ which secretes the eggshells of various worms, crustacea, mollusks, etc. -- Shell gun, a cannon suitable for throwing shells. -- Shell ibis (Zoöl.), the openbill of India. -- Shell jack…

An embryonic insect which has twice cast its skin previous to hatching from the egg.

rentiated; specifically (Biol.), homogenous, or nearly so; -- said especially of young or embryonic tissues which have not yet undergone differentiation (see Differentiation, 3), that is, which show no visible separation into their different structural parts.