Comparative anatomy / by C.Th. v. Siebold and H. Stannius ; translated from the German, and edited with notes and additions recording the recent progress of the science by Waldo I. Burnett.

  • Karl Theodor Ernst von Siebold
Date:
1854
Catalogue details

Licence: Public Domain Mark

Credit: Comparative anatomy / by C.Th. v. Siebold and H. Stannius ; translated from the German, and edited with notes and additions recording the recent progress of the science by Waldo I. Burnett. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

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    CHAPTER V. DIGESTIVE APPARATUS. § 125. With the two orders of Turbellaria, this apparatus is formed upon very different types. But in both orders, the location of the mouth varies so much, that it serves as the basis of genera, according as it is at the anterior extrem- ity, or a il’ tie behind it,—or, at the middle of the belly, or a little behind that also. The walls of the intestinal canal are always intimately blended with the parenchyma of the body. With the Rhabdocoeli, the mouth leads to a muscular oesophagus, which is either an annular sphincter, or a longer or shorter tube, but which, in no case, can be everted from the mouth. The intestinal canal is a simple cae- cum extending from the oesophagus to the posterior extremity ; but with those species which have the mouth situated more or less posteriorly, it stretches forward as a coecum to the anterior portion of the body.® With the Dendrocoeli the mouth opens into a large throat, containing a protrac- tile and very movable deglutitory organ (Pharynx). This organ, which can be protruded entirely out of the throat while the animal is eating, is either a tube comppsed of longitudinal and transverse muscles, or a collection of lobular and ramified tentacles circularly ar- ranged about the mouth. Its base is prolonged into the proper intestine, whose dendritic ramifi- cations extend over the whole body.® Scarcely a trace of salivary or hepatic organs have here been found with these animals.(3) ages on the anterior part of the body of Planaria tentaculata, and Eurylepta cornuta, and upon the neck of Planocera. With the last, they sup- port a part of the eye dots. 1 The mouth and cylindrical oesophagus of Gy- ratrix hennaphrodilus, and Vortex truncata, are at the cephalic extremity (Ehrenberg, Abhandl. d. Bcrl. Akad. 1835, p. 178, Taf. I. fig/2, 3). But the mouth and annular oesophagus of Derosto- mum is situated just back of this extremity, into which, however, the coecal intestine extends. The oesophagus is also annular with Mesostomum, and Typhloplana. In the first, the mouth is at the middle of the ventral surface ; and in the last, a little behind this point, while the intestine projects coecally far into the anterior extremity (Orsted, loc. cit. Taf. II. fig. 26, 31, and Focke, loc. cit. Taf. XVII.). - The genus Planaria has become famous for its movable organ of deglutition, which, being sepa- rated from the body, still continues for a while to swallow all presented to its mouth (Baer, loc. cit. p. * [ § 125, note 2.] With Phagocata (Planaria) gracilis, Leidy (Proceed. Acad. Nat. Sc. Phil. in. 1848, p. 248) found, instead of a single sucker, twenty-three, In the full-grown animal. These are all protruded when the animal feeds, but when not in use, are closely packed together within the animal. They all connect separately with portions of the dendritic alimentary cavity. — Ed. 716, Tab. XXXIII. fig. 8-11, and Duges, loc. cit. XV. p. 152, PI. IV. fig. 18,19). The large and plicated oesophagus of Planaria tremellaris, constitutes the transition to the ten- tacular form of the deglutitory organs (Dugds, loc. cit. XV. PI. IV. fig. 20, 21). Fully ramified ten- tacles are found with Planocera sargassicola, pellucida, and Leptoplana lichenoides. When collected in the throat, they present exactly the as- pect of a ramified intestine (Mertens, loc. cit. Taf. I. fig. 2, 3, 6, Taf. II. fig. 3, 4, and the Isis, 1836, Taf. IX. fig. 3, b. 3, c.). The ramified intestine of many Dendrocoeli has been figured by Baer, Du- g£s, and Mertens, in their works already cited.* 3 Focke (loc. cit. p. 196, Taf. XVII. fig. 11, c. f.) is inclined to regard as salivary and hepatic or- gans, two large lateral vessels, and a glandular or- gan which he has discovered near the oesophagus and intestine of Mesostomum Ehrenbergii) but he himself admits that this view is not yet well founded, t t [ § 125, note 3.] Will (Muller's Arch. 1848, p. 508) has shown that the brownish layer covering the whole extent of the intestine of Planaria is composed of hepatic glands (Dendrocoalum lac- teum, Planaria torva, and nigra). — Ed.