Books with author A. E. Sedgwick

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. 1898 Excerpt: ...-b. Gesellschaft, Mien, 1876. L. Plate, "Ectopa'r. Rotatorien d. Golfes v. Noapel," Nij,les Mil., 7, 1886 t C. Zelinka, "Die Gastrotrichen," Z. f. w. Z., 49, 1890. often prolonged into spines and hairs, a cerebral ganglion connected, with Iht: ectoderm and with, mouth and anus. The Gastrotricha (Fig. 250) are small fresh-water organisms of unknown affinities. They have a ventral mouth in front, a dorsal anus behind, and an alimentary canal presenting a muscular pharynx, stomach lined with a few large cells, and a rectum. The body cavity is indistinct, and if present is without epithelioid lining. There is no vascular system, and the excretory organs consist of two coiled tubes opening on the ventral surface, and internally ending in a ciliated portion. The ovaries are paired, and no oviducts have been observed. It is doubtful if they are hermaphrodite, and if a small median organ behind the ovaries is a testis. No male is known. There is only one kind of egg, found in summer as well as winter. The muscular system is highly developed, and in part in specialized muscular bauds. There are no transversely arranged muscular fibres. The cilia are in two ventral rows, and a patch is found on the head in the neighbourhood of the mouth. There is a dorsal ganglion in front which extends a little distance backwards on each side. The marine forms, Hemidasys Clap, and Turbanella M. Sch., appear not to be Gastrotricha. The former has a parenchyma, a well-developed testis, vas deferens, and chitinous penis, and two small ciliated pita in front like Nemertines and some Turbellarians; the ovary, nervous system, and excretory organs are unknown. In Turbanella the whole ventral surface is ciliated, and there is no chitinous cuticle; and there are two cilia...

Excerpt from A Student's Text-Book of Zoology, Vol. 1IN preparing the present work I have been actuated mainly by the desire to place before English students of Zoology a treatise in which the subject was dealt with on the lines followed with so much advantage by Claus and his predecessors in their works on Zoology. My original intention was to bring out a new edition of Claus' Lehrbuch, revised and brought up, to date, and a trace of this intention may be seen in a few pages of the present volume. But this plan was, for various reasons, soon given up, and the present treatise is, with the exception of about twenty pages, an. Entirely new work.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis 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.

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Excerpt from A Student's Text-Book of Zoology, Vol. 1In preparing the present work I have been actuated mainly by the desire to place before English students of Zoology a treatise in which the subject was dealt with on the lines followed with so much advantage by Claus and his predecessors in their works on Zoology. My original intention was to bring out a new edition of Claus' Lehrbuch, revised and brought up to date, and a trace of this intention may be seen in a few pages of the present volume. But this plan was, for various reasons, soon given up, and the present treatise is, with the exception of about twenty pages, an entirely new work.For a successful study of Zoology it is necessary that the student should begin by making a thorough examination of individual animals, of their structure, of the functions of their parts, of their relation to the external world and to each other. This method of study by types, which was largely introduced into this country by Huxley, and is admirably exemplified by that authors book on the Crayfish, is absolutely necessary as a preliminary to any thorough study of Zoology. By pursuing it the student acquires, if the animals are properly selected, a knowledge of the principal forms of animal life, and a basis from which more extended studies can be made. It is to assist these more extended studies that the present work is designed.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com

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. 1909 edition. Excerpt: ...and, in association with this feature, in the presence of free larval stages in the development; in the participation of all segments of the thorax in the formation of the cephalothoracic shield; in the short capsular heart; the absence in the adult of a lacinia mobilis on the mandible (see p. 438) (though there are indications of it in some larval stages) and in the spherical or vesicular shape of the spermatozoa. The Holotropha, on the other hand, agree with the Cumacea, Chelifera, Isopods and Amphipods in the possession of a brood pouch, in which the young are developed until the full number of appendages is attained. The terga of only the most anterior (or none? Lophogastridae), of the thoracic segments are involved in the dorsal shield, the heart is elongated, a lacinia mobilis is present, and the spermatozoa, so far as they have been observed, are filiform. The two groups also appear to be contrasted in the number of segments of the thoracic limbs, the point at which the main flexure of the limb occurs and in the possession by the limb of a terminal claw. In reviewing these differences, to several of which attention has been called by Boas and Hansen, Caiman has proposed the name Peracarida for a group containing all Eumalacostraca possessing a brood pouch, and in this the Holotropha are included, while the Hemitropha are united with the Decapoda in the group of the ' Eucarida." The division, Schizopoda, would, on this arrangement, cease to exist. While admitting that there is much to be said in favour of the course proposed, it appears preferable, in the present work, to retain the group Schizopoda. Zoologists are far from being agreed on the change, and it was strongly resisted by Claus. f Were it adopted the relations of...

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