A Student's Text-book of Zoology Volume 1
Adam Sedgwick
Paperback
(RareBooksClub.com, May 14, 2012)
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...