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The germinal membrane in an ovum, from which the embryo is developed.

Of or pertaining to the blastoderm.

pment of the ovum in which the outer cells of the morula become more defined and form the blastoderm.

Formation and separation of laminæ or layers; one of the methods by which the various blastodermic layers of the ovum are differentiated.

formative, much used in anatomical terms, and signifying skin, integument, covering; as, blastoderm, ectoderm, etc.

The outer layer of the blastoderm; the epiblast; the ectoderm.

The outer layer of the blastoderm; epiblast.

The innermost layer of the blastoderm and the structures derived from it; the hypoblast; the entoblast. See Illust. of Ectoderm.

See Endoderm, and Illust. of Blastoderm.

The outer layer of the blastoderm; the ectoderm. See Blastoderm, Delamination.

That part of blastoderm where the hypoblast appears like a small disk on the inner face of the epibladst.

and lies between these two, is sometimes included. -- Germinal membrane. (Biol.) Same as Blastoderm. -- Germinal spot (Biol.), the nucleolus of the ovum. -- Germinal vesicle, (Biol.) , the nucleus of the ovum of animals.

Alternating transparent and opaque white rings which are seen outside the blastoderm, on the surface of the developing egg of the hen and other birds.

The inner or lower layer of the blastoderm; -- called also endoderm, entoderm, and sometimes hypoderm. See Illust. of Blastoderm, Delamination, and Ectoderm.

spongy pith; pithy. Medullary groove (Anat.), a groove, in the epiblast of the vertebrate blastoderm, the edges of which unite, making a tube (the medullary canal) from which the brain and spinal cord are developed. -- Medullary rays (Bot.), the rays of cellular tissue seen in a transverse section of exogenous wood, w…

The layer of the blastoderm, between the ectoderm and endoderm; mesoblast. See Illust. of Blastoderm and Ectoderm.

central nervous system and epiderms; as, the neuroepidermal, or epiblastic, layer of the blastoderm.

(Anat.), an opaque and thickened band where the mesoblast first appears in the vertebrate blastoderm.

The outer, or parietal, one of the two lamellæ into which the vertebrate blastoderm divides on either side of the notochord, and from which the walls of the body and the amnion are developed. See Splanchopleure.

The inner, or visceral, one of the two lamellæ into which the vertebrate blastoderm divides on either side of the notochord, and from which the walls of the enteric canal and the umbilical vesicle are developed. See Somatopleure. -- Splanch`no*pleu"ric, a.