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The Biological Bulletin Volume 29 download book

یکشنبه 28 تیر 1394  05:20 ب.ظ

The Biological Bulletin Volume 29 by Marine Biological Laboratory
The Biological Bulletin Volume 29
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Author: Marine Biological Laboratory
Number of Pages: 114 pages
Published Date: 01 Mar 2012
Publisher: Rarebooksclub.com
Publication Country: Miami Fl, United States
Language: Englishhttps://d20eq91zdmkqd.cloudfront.net/assets/images/book/large/9781/2323/9781232300090.jpg
ISBN: 9781130023350
File size: 39 Mb
Download Link: The Biological Bulletin Volume 29
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915 Excerpt: ... eggs were clearly more stratified. They showed the gray cap plainly in all cases, and a hyaline zone was also recognizable in them. Thus only 25 minutes after insemination, the sperm had already begun to produce coagulative changes in the cytoplasm. From these experiments, I have been led to conclude that initiation of development, either artificially produced or the result of fertilization, always involves a gelatinization or coagulation with the egg. This coagulative change is evoked before the egg interior shows any other signs of the approach of development. The coagulating substance (or substances) is evidently very ready to coagulate. The ensemble of conditions within the egg is no doubt responsible for this unstable state. Only a slight change in salt concentration is then sufficient to bring about coagulation. The fact that both increase and decrease of salt concentration are effective, suggests that the protein involved is of the globulin type.1 The mitotic spindle probably arises as a direct result of the coagulative change. The actual explanation of how this occurs is not truly a problem of biology but a problem of colloid chemistry, for it has been shown (Fischer, '99) that coagulation of inanimate proteins can produce structures identical in appearance with the mitotic spindle. IV. Summary. 1. The unfertilized Arbacia egg consists essentially of fluid proteins, surrounded by a stiff membrane (the vitelline membrane), which is the plasma membrane of the egg cell. This membrane is a protein gel with little or no admixture of lipoids. 2. There are two types of cortical change, membrane swelling and membrane elevation. In the former, the membrane absorbs water and increases in thickness; in the latter, the normal process, it becomes lifted away fr...

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