Primitive Streak And Notochordal Canal In Chelonia

Author : Gertrude Crotty Davenport
Publisher :
ISBN 13 : 9781332044368
Total Pages : 88 pages
Book Rating : 4.0/5 (443 download)

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Download or read book The Primitive Streak and Notochordal Canal in Chelonia (Classic Reprint) written by Gertrude Crotty Davenport and published by . This book was released on 2015-07-27 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excerpt from The Primitive Streak and Notochordal Canal in Chelonia In drawing sections all outlines were made with the camera lucida. The nuclei were filled in freehand, except in a few instances in which it was deemed expedient to use high magnification. In these instances the outline of every cell, nucleus, and yolk globule was faithfully drawn by means of the camera. Those therefore who disagree with my interpretation of facts may at least have conditions faithfully reproduced upon which to base their own explanations. II. Scope of the Paper. The scope of this paper is narrow. Not all the questions upon which my sections throw light are discussed. The question, concerning the homologies of the notochordal invagination is purposely avoided for the present. Some observations, however, have been made upon the manner in which the invagination of this canal takes place. My sections also throw some light upon the question controverted between Will and Mitsukuri concerning the length and width of the notochordal canal. The facts which these sections afford lead me to agree in this matter with Wills theoretical conclusions. The much contested question concerning the origin of the mesoderm will not be considered in the present paper. However much Will and Mitsukuri may disagree as to the manner of it, they both testify to the fact that the gastral mesoderm (Rabl, '88, p. 660) arises from the entoderm lateral to the chorda, therefore they both furnish evidence for Hertwigs coelom theory. Their point of disagreement seems scarcely to warrant the words already spent upon it. Some of my series give me that condition which Mitsukuri ('91, p.199) considers as positive evidence of coelomic outpocketings, while in other series the Zwischenplatte appears solid and flat. Concerning the homology between the Rusconian plug of Amphibians and a clump of cells behind the blastopore of Reptilia, I find myself in agreement with Robinson and Assheton ('91, p.477), Keibel ('93, p.105), and Bonnet('91, pp. 78, 79). About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.