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.

    47/482 (page 43)
    CHAPTERS III. AND IV. NERVOUS SYSTEM AND ORGANS OF SENSE. §33. As yet only a very rudimentary and imperfectly distinguished nervous system has been made out in the Polyps ; this consists of round masses, which are regarded as composed of nervous matter (ganglia), situated in the parenchyma. A ganglion of this kind has been supposed to have been observed about the mouth.™ §34. Investigations upon their organs of sense have rrot been more suc- cessful. However, the sense of touch appears developed over the whole surface of the body, but specially so in the extremely irritable arms and tentacles. But, as yet, no tactile nerves have been found in these parts. In the same manner, light, to which these animals show a greater or less sensibility, is perceived rather by the general surface of the body than by special organs. There are, however, in some species, at particular stages of development, during which they swim freely about, certain nicely-defined bodies situated upon the sides of the body, and which may be regarded as special organs of light and sound. This is the case with Syncory^e ;(I) and Coryne(2) has in their place four red organs which correspond exactly to those found on the border of the disc of the pulmograde Acalephre, and which have been re- garded as organs of sense. The organ seen at the base of the six arms of Eleutheria dlchotorna has quite the appearance of an eye ; that is, there can be distinguished in 1 A double oesophageal ganglion has been ob- served by Dumortier (Mem. sur V Anat. et la Physiol, d. Polypiers composes d’eau douce 1836, p. 41, pi. II. fig. 2) in Lophopus cristallinus (Pin- mateila cristata of Lamarck); and by Coste (Comp. rend. XII. 1841, p. 724)in the Plumatel/ae in general. Nordmann also has seen a similar ganglion under the mouth of PInmatella campa- nulata (Lamarck) (loc cit. p. 709), and of Teadra zostericola (Ann. d. Sc. Nat. XI. 1838, p. 190). According to Kan Beneden, a nervous ring sur- rounds the oesophagus of ALcyonella (Ann. d. Sc. * [§ 33, note 1.] Allman has observed with Cristatella mucedo a small roundish body situated at the upper end of the pharynx, and which he re- gards as a nervous ganglion (Rep. Brit. Assoc. Ad- vancem. of Sc. 1846, p. 88). This observation he subsequently confirmed, and has observed with Plamaltlla repens this ganglion ( which he terms the great oesophageal ganglion) send off a large filament to each of the tentaculiferous lobes ; also a smaller one passing off at each side to embrace the oesophagus, while a very short one was distrib- Nat. XIV. 1840, p. 222). Coste asserts the presence of a nervous system in Pennatula (Proriep's neue Notizen, 1842, No. 450, p. 154). That which Spix pretended to have discovered in the foot of Acti- nia (Ann. d. Mus. d’llist. Nat. 1809, p. 443, pi. XXXIII. fig. 4) has been properly rejected by most modern zootomists, as au illusion. See Ber- thold, loc. cit. p. 6.* 1 Lov^n, fViegmann's Arch. 1837, I. p. 323. 2 Steenstrup, Ueber den Generationswechsel, p. 23. uted in the substance of this last organ. And, finally, another set of filaments were distributed to the organs about the mouth. See Report of the same, for 1849, p. 72. According to a late Report, this observer appears to have been able to make out a distinct nervous system in all the fresh-wa- ter Bryozoa, except Paludicella. He has, how- ever, been able to detect no certain organ of spe- cial sense. See report of the same for 1850, p. 319. —Ed.