Amphioxus Vertebrata

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. 1894 edition. Excerpt: ...in the details of its organisation, essentially resembles the embryos of the higher types. GENERAL CONSIDERATIONS. We will now pass on to give a general interpretation of some of the principal phenomena which are presented to us in the development of Amphioxus. Larval Asymmetry. By far the most prominent feature of the fully formed larva is its astounding asymmetry, and it is extremely important, from a morphological point of view, to form a just conception of it. The phenomenon of asymmetry manifests itself in the larva of Amphioxus under several very different aspects, and is occasioned by various causes. For convenience we may classify the forms of asymmetry which we have to consider under three main divisions, according to the type of organs involved. 1. Median Asymmetry.--This relates to such structures as lie normally in the middle line, whether dorsal or ventral, but which have been mechanically or correlatively displaced from their primitive position by the differential growth of neighbouring parts. Such are the olfactory pit and neuropore, the anus, the mouth, and the endostyle. All these are essentially and primordially median and unpaired structures. We have already dealt with the neuropore and anus, while the mouth and endostyle will be considered below. 2. Bilateral Asymmetry.--This refers to the alternation of paired structures, such as myotomes, spinal nerves, gillslits, and gonads, which we have already noted in the adult organisation. Primarily the organ of one side lies opposite to its antimere of the other side. By a secondary displacement it comes to alternate with it. 3. Unilateral Asymmetry.--Next to the asymmetrical mouth, this is perhaps the most striking form of asymmetry which the larva of Amphioxus exhibits. It...

This work has been selected by scholars as being culturally important and is part of the knowledge base of civilization as we know it. This work is in the public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. To ensure a quality reading experience, this work has been proofread and republished using a format that seamlessly blends the original graphical elements with text in an easy-to-read typeface. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.

This work has been selected by scholars as being culturally important and is part of the knowledge base of civilization as we know it. This work is in the public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. To ensure a quality reading experience, this work has been proofread and republished using a format that seamlessly blends the original graphical elements with text in an easy-to-read typeface. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.

This is a reproduction of a book published before 1923. This book may have occasional imperfections such as missing or blurred pages, poor pictures, errant marks, etc. that were either part of the original artifact, or were introduced by the scanning process. We believe this work is culturally important, and despite the imperfections, have elected to bring it back into print as part of our continuing commitment to the preservation of printed works worldwide. We appreciate your understanding of the imperfections in the preservation process, and hope you enjoy this valuable book.

This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work was reproduced from the original artifact, and remains as true to the original work as possible. Therefore, you will see the original copyright references, library stamps (as most of these works have been housed in our most important libraries around the world), and other notations in the work. This work is in the public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work.As a reproduction of a historical artifact, this work may contain missing or blurred pages, poor pictures, errant marks, etc. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.