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

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 IX. ORGANS OF GENERATION. § 140. Although it is certain that the Rotatoria propagate only by genital organs, yet the female organs only are yet well known. These consist of a single or double ovarian tube of variable length, situated upon the sides of the intestinal canal at the posterior part of the cavity of the body, and opening into the cloacal cavity through a short oviduct. These ovaries never develop but a few eggs at a time. The mature eggs are always oval and surrounded by a simple, solid, colorless envelope. They contain a finely granular and usually colorless vitellus, in which there is a distinct germinative vesicle. Many species are ovigerous, but a few only are vivi- parous. a) It would be naturally supposed that these animals, which have such dis- tinct female organs, would have also those of the other sex. But as yet the most minute researches have failed to detect them. It is therefore doubt- ful whether these animals are hermaphrodites or of separate sexes.t<2> 1 For the various forms of the ovaries see the classical works of Ehrenberg. With Philodina roseola, Brachionus rubens, and Mastigocerca carinata, the vitellus of the eggs as well as the parenchyma of the body is of a reddish color. With those species which live in the tubes, the eggs are usually deposited in the cavity of these last. But with Triartkra, Polyarthra, and Brachionus, they remain glued to the cloacal opening. With Philodina, the young are often hatched in the cavity of the parental body, and are, accord- * [ § 140, note 1.] The view here expressed that the young of the viviparous Philodinae may find their escape from the body of the parent through an opening near the anus — the oviducts being perhaps wanting— is probably correct, since, in the viviparous Aphides, where the processes of repro- duction occur likewise by a kind of gemmiparity, there are, according to my observations, no ovi- ducts proper, but the young, having fallen into the abdominal cavity, thence escape through a Porus genitalis situated near the anus. — Ed. t {End of § 140.] The discovery of distinct males with the Rotatoria is due to Brightwell (Ann. Nat. Hist. Sept. 1848) who has positively determined it with Asplanchna. Here it is about half the size of the female, being also of a different form; it is exceedingly transparent and easily eludes observation. The testis appeared as a round ves- sel situated at the bottom of the body on one side, and filled with spermatic particles. This author 13* ing to Ehrenberg (Die Infusionsthierchen p. 483), always surrounded with an extensible membrane of the ovary (uterus). But it has always appeared to me that the mature eggs of the viviparous Phi- lodinae, are detached from the ovaries and fall into the cavity of the body, where afterwards the hatched young move about. Perhaps oviducts are here wanting and the young escape from their parent through an orifice near the cloacal open- ing.* ^ Admitting that there are here male genital organs, the respiratory tube upon the neck of thinks also that he observed a well-defined intro- mittent organ connected with the testis, and a passage for its extension from the body of the animal. In verification of this observation it may be men- tioned that Brightwell observed the actual coitus between the sexes, and Gosse (loc. cit. p. 22) has witnessed the development of the males from the ovum. Huxley, on the other hand (Quat. Jour. Mic. Sc. No. I. Oct. 1852, p. 1), has found with Lacin- ularia no trace of a male individual, but in some specimens he observed singular bodies which answered precisely to Ko/li/cer's description of the spermatic particles of Megalotrocha. He says, “ They had a pyriform head about 1-1000 in. in diameter by which they were attached to the parietes of the body, and an appendage four times as long which underwent the most extraordinary contor- tions, resembling however a vibrating membrane$