. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. EXOGASTRULATION AND RELATED MODIFICATION-. 75 its chief axis at a glance. Here the manifestations of li are tir-t visible at the animal pole or apex and pn>^: dually and towards the basal region which is reached l,i~i, often hour- .tfter the opposite end had been affected. The apparent n-ver-e in some slow-acting solutions was obviously due eiiiin-ly to the basal extrusion of the mesenchyme. Tin- same gradient persists into the gastrula stage, where the apex -hows the greatest susceptibility,
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. EXOGASTRULATION AND RELATED MODIFICATION-. 75 its chief axis at a glance. Here the manifestations of li are tir-t visible at the animal pole or apex and pn>^: dually and towards the basal region which is reached l,i~i, often hour- .tfter the opposite end had been affected. The apparent n-ver-e in some slow-acting solutions was obviously due eiiiin-ly to the basal extrusion of the mesenchyme. Tin- same gradient persists into the gastrula stage, where the apex -hows the greatest susceptibility, while the inva^inated • •MI.,derm is so much more resistant (except probably for a /one around the blastopore) that it usually survives in M [OO KNC an hour or more after the ectoderm of the entire gastrular \\all has disintegrated. By returning non-disintegrating gastrula1 to sea water after an appropriate exposure the ensuing dish ion may be checked midway in its course and recovery \.r olit,lined showing absence or partial loss of apical (or even nioir basal) ectoderm and more or less complete survival of the ento- dermal parts which are accordingly large in proportion to the whole. As in the case of Arbacia "in the gastrula the apex of the conical both' represents the apical end of the major axis, and the Mastopore the basal end, while the entoderm represents a still more basal region of the egg and blastula, and the mex in livme the most basal region" (Child, 'ib/>, pp. 68-69). Vital staining with neutral red and other basic dyes shows an apico-ba-al progression in and early gastruhe quite paralleling in all essentials the wave of advancing disintegration as de-cribed above. The experimental embryologists have described the i-oinni"n. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
