A student's text-book of zoology Volume 2 - Softcover

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: ... Saccobdella v. Ben. and Hesse. Fio. 250.--Vhaetonotw maximut (after Biit-GASTROTRICHA. t Mchli), ventral view. Cb row of cilia; Oe oesophagus. Small aquatic organisms with a double ventral row of cilia, a cuticle C. Clans, "Ucb. die Organisation, eta, der Gattung Seison," Festschrift z. F. d. 26 j. Best. d. K. k. z. b. GeselUeha.fi, Wien, 1876. L. Plate, "Ectopar. Rotatorien d. Golfes v. Xeapcl," Naples Mit., 7, 1886 t C. Zelinka, "Die Gastrotrichcn," Z. f. w. Z., 49, 1890. often prolonged into spines and hairs, a cerebral ganglion connected with the ectoderm and with mouth and anus. The Gastrotricha (Fig. 250) are small fresh-water organisms of unknown affinities. They have a ventral month 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. Thero is only one kind of egg, found in summer as well as winter. The muscular system is highly developed, and in jiart in specialized muscular bands. There are no transversely arranged muscular fibres. The cilia are in two ventral rows, and a jiatch 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, HemicUisys Clap, and Turbrmclla M. Sell., appear not to be Gustrotrkhn. The former h...