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
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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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    is quite remarkable with those species whose single or double disc is not crenulate, but entire.® With those whose organs are more numerous, but smaller, this appearance is not observed.® With Floscularia, and Stephanoceros, the rotatory organs have quite a different form. With the first, there are five or six button-like processes about the mouth, covered with very long bristles; these bristles produce usually but very feeble motions, and rarely give rise to vortexes. But Ste- phanoceros reminds one much of the Bryozoa, for its rotatory apparatus con- sists of five tentacle-like processes covered with vibratile cilia® The rota- tory organs differ, moreover, from the ordinary vibratile cilia of epithelium, in being under the animal’s control, — that is, moved or kept at rest, at will.® CHAPTERS III. AND IY. NERVOUS SYSTEM AND ORGANS OE SENSE. § 134. Notwithstanding the transparency of the Rotatoria, and the distinctness with which their organs are separated from each other, yet their nervous system has not yet been made out with certainty, for their bodies are so small that their peripheric nerves elude the microscope, and their principal nerves and ganglia cannot be distinguished from the muscular fasciculi, the liga- ments, and the contractile parenchyma of the body. It appears certain, however, that in all, there is, as a nervous centre, a group of cervical ganglia, from which pass off threads in various direc- tions.® 1 Conochilus, Philodina, and Actinurus. 2 Htjdatina, Notommata, Synchaeta, and Dig- lena. 3 See Ehrenberg, Die Infusionsthierchen, Taf. XLV. 4 According to Ehrenberg, there are, at the base of each cilium of the rotatory organs, many striated muscles, which, acting antagonistically, produce the motion (Abhandl. d. Berl. Akad. 1831, p. 34). But neither Dujardin (Infusoires, loc. cit. p. 579), nor Rymer Jones (Compar. Anat. &c. p. 120), has been able to perceive this apparatus. The contractile parenchyma on which the virbra- tile discs are situated, appears to be destined only for the protrusion and retraction of the rotatory organs.* 1 Ehrenberg, to whom we are indebted for our chief information upon the nervous system of these animals, first took for a cerebral ganglion the gland- * [ § 133, note 4.] Dobie (Ann, of Nat. Hist. 1848) speaks of two kinds of cilia with Floscularia; “ one of the usual short vibratile kind, covering the inte- rior of the alimentary tube 5 the other extremely uliform body found upon most Rotatoria, and in the neck of Hydatina senta, and Notommata col- laris (Abhandl. d. Berl. Akad. 1830, p. 52, Taf. Yin. 1833, p. 189, Taf. IX., and, Die Infusionsthier- chen, p. 386, &c.). Besides this ganglion, he has mentioned with Hydatina, Synchaeta, and Dig- lena, many others scattered through the anterior part of the body, and connecting with the cerebral one by nervous filaments. Likewise, with Enter- oplea, Hydatina, Notommata, and Diglena, he has regarded as a nervous loop, the two filaments which pass off from the cerebral ganglion, and go to the cervical respiratory orifice. Finally, he refers to the sensitive system, a white sacculus, single or double, and situated behind the cerebral ganglion, with Notommata, Diglena, and Theorus (Die Infusionsthierchen, p. 425). Grant's description of the nervous system of the Hydatina, as being composed of many ganglia and a ventral cord. long and filiform, of uniform thickness, and not vibratile under ordinary circumstances.” They are slowly moved, being spread out by the contractile substance of the lobes of the rotatory organ. — Ed.