Lanterna Rally

Author: Eugene Howard Harper

Publisher:

Published: 2015-08-08

Total Pages: 54

ISBN-13: 9781332481590

Excerpt from The Fertilization and Early Development of the Pigeon's Egg: A Dissertation Submitted to the Faculties of the Graduate Schools of Arts, Literature, and Science, in Candidacy for the Degree of Doctor of Philosophy; Zoology About the early development of the large meroblastic eggs comparatively little is known. This has remained true in spite of the thoroughness with which the embryonic stages of selachian and chick have been studied. As a result of the work of a number of investigators, chiefly Biickert, there is now a fairly complete general survey of the fertilization and early stages of the selachian egg. Observations upon the early development of the birds egg are very few. Some of the early cleavage stages of the chick were figured by Coste, and Balfour contributed some observations. The internal phenomena of the egg during maturation, fertilization and early cleavage have remained an open field for investigation. Upon the ovarian history of the bird? egg observations have been quite numerous. The paper of Holl, 90, upon the hen's egg may be mentioned as one of the most important. The development of the large meroblastic eggs obviously presents numerous problems. In this paper the stages of the obtained are scattered over a considerable period, and present glimpses of various phases of maturation, fertilization and early cleavage. A few stages of the ovarian egg have also been introduced. Methods. The method followed has been to fix the whole egg before attempting to remove the germinal area. The oviduct is removed, the position of the egg being carefully noted, as this enables one to judge the approximate stage in development and determines the subsequent treatment in staining. The portion of the oviduct containing the egg is then cut off, immersed in the fixing fluid and slit open underneath the liquid. In case of an egg which is free in the body cavity, with some caution the. body may be inverted over the fixing fluid, allowing the egg to drop out. The large ovarian egg may be fixed long enough to allow the fluid to penetrate the disc, then hardened in alcohol and the germinal area subsequently dissected out. The choice of fixing fluids is somewhat limited, since many of them leave the disc too brittle to stand the subsequent treatment, and washing in water is undesirable. The picro-acetic mixtures have been chiefly used. Long fixation is not necessary or desirable, owing to the swelling of the yolk, which is apt to distort the disc. 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.