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simple auditory organs of many invertebrates, containing a fluid and otoliths; also, the embryonic vesicle from which the parts of the internal ear of vertebrates are developed.

The penis or clitoris, or the embryonic or primitive organ from which either may be derived.

In embryonic development, a vesicle filled with fluid, formed from the morula by the divergence of its cells in such a manner as to give rise to a central space, around which the cells arrange themselves as an envelope; an embryonic form intermediate between the morula and gastrula. Sometimes used as synonymous with ga…

The embryonic shell, or first chamber, of ammonites and other cephalopods.

One of the primary, or first-formed, segments of an embryonic arthropod.

The embryonic sac of an ovule, sometimes regarded as an innermost fifth integument. Cf. Quartine, and Tercine.

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 embryo sac or embryonal vesicle in the ovules of flowering plants.

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.