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.

    67/482 (page 63)
    CHAPTER III. NERVOUS SYSTEM. §59. A nervous system has been found in many Acalephae. With the Cteno- phora the oesophagus is surrounded by a ring formed of eight ganglia,® and at the opposite extremity of the body there is a simple ganglion. Five nervous filaments pass out from these ganglia, and along the sides of the body are nervous fibres, which ultimately divide into delicate threads.® The tentacles of Medusae are supplied with nervous filaments which issue from a ganglion situated at their base.® CHAPTER IV. ORGANS OE SENSE. § 60. With many Acalephae, there are, upon the borders and extremities of 1 These eight ganglia, which are connected together by delicate cords, were first observed by Grant (Trans. Zool. Soc. Lond. I. p. 10) in Cydip- pe pileus. Compare, also, Wagner, Icon. zoot. Tab. XXXIII. fig. 37, A. B. From each of these ganglia two nerves pass off to the side, while a third, traversing the interior of the body, and hav- ing two or three swellings, is finally distributed to the intestine. Patterson (The Edin. new Philos. Join’. XX. p. 26), and Forbes (Ann. of Nat. Hist. 1839, p. 145), have also observed the oesophageal ring in Cydippe, but did not perceive the ganglia. 2 Milne Edwards (Ann. des Sc. Nat. loc. cit. I). 206, PI. IY. fig. 1) has observed at the poste- rior extremity of the body of Lesueuria vitrea (a new Bero'id) a ganglionic body which sends * [ § 59, note 3.] The nervous system of the Acalephae has been successfully studied by Agassiz upon several genera (Hippocrene, Tipropsis, Staurophora). His results are new, and different from those of previous observers. I cannot do bet- ter than to quote his words: “There is, unques- tionably, a nervous system in Medusae, but this nervous system does not form large central masses, to which all the activity of the body is referred, or from which it emanates. There is no regular com- munication by#nervous threads between the centre and periphery and all intervening parts *, and the nervous substance does not consist of heterogene- ous elements, of nervous globules and nervous threads, presenting the various states of complica- tion and combination, and the internal structural differences, which we notice in the vertebrated ani- mals, or even in the Mollusca and Articulata.” out in front four filaments ; and upon the sides of this animal a nervous cord, from which pass off delicate branches at regular intervals. At the pos- terior extremity of the body of Cydippe, Eucha- ris and Medea, Will (Froriep's neue Notizen, No. 599, 1843, p. 67, and Horse tergest. p. 44) has likewise observed a round, yellowish ganglion, with four prolongations, from which pass off twenty-five or thirty nerves. ;i Ekrcnberg has found along the entire border of the disc of Medusa aurita, and between each two tactile filaments, a bifid nervous ganglion. He affirms to have seen also two others similar, at the base of each tentacle surrounding the genital organs. See Abhandl. d. Berl. Akad. 1835, p. 203, Taf. IV. fig. 1, x.-, and Muller'1 s Arch. 1834, p. 571.* “ In Medusae the nervous system consists of a simple cord, of a string of ovate cells, forming a ring around the lower margin of the animal (PI. Y. fig. 11, 2, 4, 5), extending from one eye-speck to the other, following the circular chymiferous tube, and also its vertical branches, round the upper portion of which they form another circle. The substance of this nervous system, however, is throughout cellular, and strictly so, and the cells are ovate. There is no appearance in any of its parts of true fibres” (loc. cit. p. 232). That this is the nervous system seems placed beyond all controversy -, for, in a private letter, Agassiz has informed me that in a new genus (.Rhacostoma), living on the shores of Massachusetts, he has seen this system at night as an illuminated diagram. — Ed.