«§.^ 33, 34. 



THE POLYPI. 



43 



CHAPTERS III. AND IV. 



NERVOUS SYSTEM AND ORGANS OP 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 Acalephae, and which have been re- 

 garded as organs of sense. 



The organ seen at the base of the six arms of Eleiitheria dichotoma 

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



1 A double oesophageal ganglion has been ob- 

 served by Diimortier (Mem. sur I' Anat. et la 

 Physiol, d. Polypiiji's composes d'eau douce 1836, 

 p. 41, pi. II. fig. 2) in Lopliopux crislallinim (P/u- 

 matella cristata of Lamarck) ; and by Coste 

 (Comp. rend. XII. 1841, p. 724)in theP/u/Ha<e«ae 

 in general. Nordmann also has seen a similar 

 ganglion under the mouth of Plumatella campa- 

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

 zostericola (Ann. d. So. Nat. XI. 183S, p. 190 ). 

 According to f^an 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 (Hep. Brit. Assoc. Ad- 

 vancem. of Sc. 1846, p. 88). This observation he 

 subsequently confirmed, and has observed with 

 Plumatella 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 (Esophagus, while a very short one was distrib- 



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

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

 Notizen, 1842, No. 450, p. 154). That which Spix 

 pretended to have discovereil in the foot of Acti- 

 nia (Ann. d. Mus. d'llist. Nat. 1S09, p. 443, pi. 

 XXXIII. fig. 4) has been properly rejected by 

 most moJern zootomists, as an illusion. See Ber- 

 thold, loc. cit. p. 6.* 



1 Lov^n, Wiegmann'H 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. 



