from The Century Dictionary.
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- adjective biology Of or relating to the
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adjective of or relating to the ectoderm
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Their skin is merely a layer of ciliated ectodermic cells.
(Figure 1.73 A) leads to the formation of an eccentric cavity, the group of the darker entodermic cells (hy) remaining directly attached at one spot with the round enveloping stratum of the lighter ectodermic cells (ep).
The acoustic nerve is formed from ectodermic cells of the hind brain, and develops from the nervous structure that appears at its dorsal limit.
While the medullary groove is sinking in the middle line of the flat dorsal side of the oval embryo, and its parallel edges unite to form the ectodermic neural tube, the single chorda is formed directly underneath them, and on each side of this a parallel longitudinal fold, from the dorsal wall of the primitive gut.
The placenta is formed by the branches of the blood-vessels in the wall of the allantois growing into the hollow ectodermic tufts (villi) of the chorion, which run into corresponding depressions in the mucous membrane of the womb.
When we come to the higher Metazoa, in which the sensory functions and their organs are more advanced, we find a division of labour among the ectodermic cells.
The real wall of the vesicle enclosed by it consists of a simple layer of ectodermic cells (b), which are flattened by mutual pressure, and generally hexagonal; a light nucleus shines through their fine-grained protoplasm (Figure 1.108).
A section through the embryo in the hatched hen's egg towards the close of the first day of incubation shows in the middle of the dorsal surface a broad ectodermic medullary groove (Figure 1.92 Rf), and underneath the middle of the chorda (ch) and at each side of it a couple of broad mesodermic layers (sp).
Its globular blastula (Figure 1.45) consists of loosely-aggregated, yelk-filled entodermic cells or yelk-cells (dz) in the lower vegetal half; the upper, animal half encloses the hemispherical segmentation-cavity (fh), the curved roof of which is formed of two or three strata of small ectodermic cells.
(From Selenka.) a animal pole of the blastula, v vegetal pole, en mother-cell of the entoderm, ex ectodermic cells, s spermia, ib unnucleated yelk-balls