^^ 33, 34. TUE POLYPI. 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 not 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 Syncoryne ;^^^ and Coryne^^^ has in 

 their place four red organs which correspond exactly to those found on the 

 border of the disc of the pulmograde Acalephse, and which have been re- 

 garded as organs of sense. 



The organ seen at the base of the six arms of Eleutheria dlcliotoma 

 has quite the appearance of an eye ; that is, there can be distinguished in 



1 A double oesophageal ganglion has been ol> Nat. XIV. 1840, p. 22'2). Coste asserts the presence 



BerveJ by Dumortier (Alem. sur 1' Anat. et la of a nervous system in Pennatula (t^roriep's neue 



Physiol, d. Polyphrs composes d'eau douce 1836, Notizen, 1842, No. 450, p. 154). That which 5;)iar 



\>.il, \>\. U. fig. 2) in Lophopas cristallinus (Plu- pretended to have discovered in the foot of Act i- 



matelia cristata of Lamarck); and by Coste n;« (Ann. d. Mus. d'Hist. Nat. 1809, p. 443, pi. 



(Comp. rend. XII. 1841, p. 724)in the P/Mma<e//ae XXXIII. fig. 4) has been properly rejected by 



in general. Nordmann also has seen a similar most modern zootomists, as an illusion. See ßer- 



ganglion under the mouth of Plumatella campa- tliold, loc. cit. p. 6.* 



nulata (Lamarck) (loc cit p. 709), and of Tendra 1 Lov^n, Wiegmann's Arch. 1837, 1, p. 323. 



zostericola (Ann. d. Sc. Nat. XI. 1838, p. 190). 2 iveeri.^fru;), Ueber den Generationswechsel, p. 



According to Fan Beneden, a nervous ring sur- 23. 

 rounds the oesophagus of ALcyoneUa (Ana. d. Sc. 



* [ § 33, note 1.] Allman haa observed with uted In the substance of this last organ. And, 



Cristatella mucedo a small roundish body situated finally, another set of filaments were distributed tj 



at the upper end of the pharynx, and which he re- the organs about the mouth. See Report of the 



gards as a nervous ganglion (Rep. Brit. Assoc. Ad- Eame, for 1849, p. 72. According to a late Report, 



vancem. of Sc. 1846, p. 88). This observation he this observer appears to have been able to make 



subsequently confirmed, and has observed with out a distinct nervous system in all the fresh-wa- 



P/uma^e/to rejaens this ganglion ( which he terms ter Bryozoa, except Paludicella. He has, how- 



the great oesophageal ganglion) send off a large ever, been able to detect no certain organ of spe- 



filament to each of the tentaculiferous lobes ; also cial sense. See report of the same for 1850, p. 



a smaller one passing off at each side to embrace 319. — Ed. 

 the oesophagus, while a very short one was distrib- 



