<^§ 33, 34. 



THE POLYPI. 



43 



CHAPTERS III. AND IV. 



NERVOUS SYSTEM AND OEGANS 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 Syiicoryne ;^^^ and Corijne^'-^ has in 

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

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

 garded as organs of sense. 



The organ seen at the base of the six arms of Eleutheria dkhoto'ma 

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



1 A double cBsophageal ganglion has been ob- 

 served by Dumortier (Mem. sur 1' Anat. et la 

 Physiol, d. Polypiers composes d'eau douce 1836, 

 p. 41, pi. II. fig. 2) in Lophopus crista/linus (P/u- 

 matella cristata of Lamarck) ; and by Cosle 

 (Comp. rend. XII. 18-11, p. ' li)inthe Plumatellae 

 in general. Nordmann also has seen a similar 

 ganglion under the mouth oi Ptumatella campa- 

 nulata (Lamarck) (loc cit p. 703), and of Tendra 

 zostericola (Ann. d. Sc. Nat. XI. 1838, p. 190 ). 

 According to Fan Beneden, a nervous ring sur- 

 rounds the oesophagus of Alcyonella (Ann. d. Sc. 



* [§ 33, note 1.] dUman has observed with 

 Cristatella mucedo asmall 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 

 Plumatella repens this gangUon ( which he terms 

 the great oesophageal ganglion) send ofif a large 

 filament to each of the tentaculiferous lobes ; also 

 a smaller one passing off at each side to embrace 

 the cesophagus, while a very short one was distrib- 



Nat. XW. 1840, p. 222). Coste asserts the presence 

 of a nervous system in Pennatula {Froriep''s neue 

 Notizen, 1342, No. 450, p. 154). That which Spix 

 pretended to have discovered in the fx)t of Acti- 

 nia (Ann. d. Mus. d'Uist. Nat. 1809, p. 443, pi. 

 XXXIII. fig. 4) has been properly rejected by 

 most modern zootomists, as an illusion. See Ber- 

 tho/d, loc. cit. p. 6.* 



1 Lov^n, me^mann's Arch. 1837, 1, p. 323. 



2 Steenstrup, Uebei' den Generalionswechsel, 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 Paludice/la. 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. 



