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The Elementary Principles of General Biology (Paperback) Loot Price: R466
Discovery Miles 4 660
The Elementary Principles of General Biology (Paperback): James Francis Abbott

The Elementary Principles of General Biology (Paperback)

James Francis Abbott

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Loot Price R466 Discovery Miles 4 660

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1914 edition. Excerpt: ... organism. There appears to be every gradation in the degree of such differentiation. In some cases there is apparently none at all. In others, different zones or strata may be seen. In many such eggs mutilation of certain parts of the egg-cell produces corresponding defects in the resultant organism, showing that the protoplasm was already specifically differentiated before cleavage. The amount and distribution of the food-yolk is of the greatest influence in determining the nature of the cleavage process. In an isolecithal egg the first cleavage usually divides the egg-cell into two approximately equal daughter-cells, which, in turn, divide, each into two others of about the same size. This process is repeated in rapid succession until the original zygote has been halved, quartered, and then cut into 8, 16, 32, 64, 128 cells, etc., the process continuing until the first step in differentiation occurs. The result of such repeated cell division is a rounded mass of tiny cells that looks somewhat like a mulberry, and, for that reason, the stage is often called the morula. In very few species, however, is the process of cleavage so regular and symmetrical as just described. In many forms, not only are the cells of a different size, but the cleavages do not all occur in regular order, some coming on faster than others. In nearly all cases, however, the result of the continued cleavage is to produce a mass of cells that remain attached to one another in a single layer. Owing perhaps to the stress of surface tension acting on the cells and pulling them away from the center, the resultant is a hollow sphere. The stage just described is called the blastula. The closed cavity surrounded by the single layer of cells (blastomeres) is called the...


Imprint: Rarebooksclub.com
Country of origin: United States
Release date: October 2012
First published: October 2012
Authors: James Francis Abbott
Dimensions: 246 x 189 x 4mm (L x W x T)
Format: Paperback - Trade
Pages: 72
ISBN-13: 978-1-151-85781-1
Categories: Books > Science & Mathematics > Science: general issues > General
LSN: 1-151-85781-5
Barcode: 9781151857811

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