160 THE ANNELIDES. ^ 149. 



With the Dorsibranchiati, the many delicate threads which arise from 

 the cerebral ganglion by special roots and pass to the different portions of 

 the digestive canal with a ganglion here and there upon their course, may 

 be regarded as splanchnic nerves. '^■^' 



With the Amphinoniae, Euniceae, Nerei'deae and Ariciae, there arise 

 from the posterior border of the cerebral ganglion two roots which may be 

 regarded as Nervi pharyngei superiores, and which unite near their origin 

 into a GaJigUon pkaryngeum siiperius. From this last pass off posteriorly 

 delicate threads which form many ganglia upon the oesophagus, and after- 

 wards spread over probably many other parts of the digestive canal. 



Beside this Plexus splanchniciLS superior, there is sometimes a Plexus 

 splanchnkus inferior — formed by other roots which pass off inferiorly 

 from the brain ; part of these form under the ojsophagus a Ganglion pka- 

 ryngeum inferius, while others, passing backwards, constitute Nervi pha- 

 ryngci and cesophagei.^^'^^ 



The Aniphinomae have on each side of the abdomen a very remarkable 

 ganglionic chain. Their ganglia intercommunicate, not only by longitudinal, 

 but also by transverse anastomoses, with the central mass of the nervous 

 system. Among these last, those which are given off from the anterior 

 lateral ganglia, join the connecting filaments of the oesophageal ring ; while 

 the others, arising from the posterior lateral ganglia, go to the various 

 ganglionic enlargements of the ventral cord.^^'^ 



It has not yet been possible to ascertain the signification of these lateral 

 ganglionic chains. 



CHAPTER IV. 



ORGANS OF SENSE. 



I. Organs of Touch. 



§ 149. 



With the Annelides, the sense of touch is particularly developed at the 

 cephalic extremity. '^^ With some Lumbricini, this extremity is prolonged 

 into a kind of tentacular proboscis.^-' The Branchiati have special and 



15 Cuvier (Lee. d'Anat. Comp. II. 337) has no- 17 These two ganglionic chains were first de- 

 ticed with Aphrodite two nerves passing back- scribed by Stannius with Amphinome rostrata 

 wards wiuch ouglit to be regarded as of a splanch- (Isis, 1831, p. 9S6, Taf. VI. fig. 4). He saw three 

 nic nature; but Grube (Zur. Anat. d. Kiemen- ganglia connect with the oesophageal ring on each 

 wiirmer, p. 58) has been unable to fi^d them even .side. But Grube (De Pleione carunculata, p. 10, 

 in the same species. fig. 5) has seen six on each side with Amphinome 



16 Stannius (Isis, 1831, p. 983, Taf. VI. fig. 8, r. carunculata. These lateral gangUa, moreover, 

 r.), and Grube (De Pleione carunculata, 1837, p 9. remind one of those described by fVazner, as al- 

 fig. 5, r.), have seen with certain species of Amphi- ready noticed with Pontobdella muricata. 

 name the two roots of t\K Plexus splanchnicus 1 According to liathke (Danzig. Schrift. loc. cit. 

 superior, but were unable to trnci' them further, p. 94, 100), the two cephalic and respiratory fossae 

 However, with Eunice H/irassii, Grube (Zur. with the Nemertini, are the seat of a most delicate 

 Anat. d. Kiemenwiirmer, p. 43, Taf. II. fig. 9,i.)ha3 sense of touch ; and their white, long and protrac- 

 found beside these two roots, the G'rtnA'/ion yAnri/n- tile probi)Scis is also a tactile organ. But other 

 geum superius which they form, and the nervous naturalists attribute wholly different functions to 

 filaments which pass off from this last. Quite lately, these organs. 



Quatrefa^^e.i has given very exact and detailed "^ The proboscis is non-articulated with Ifals pro- 



descriptions and figures of the exjiansions of the boscidea, and Eaaxes Jiliformis (Grube, fVies- 



Plexus splanchnicus superior -Aud inferior, V!\ih. mannas Arch. 1844, 1. p. 204, Taf. VII. fig. 1). 



Eunice Nereis, Glycrra, Ph>jllodoce,-M\A Arid- But it is articulated with Rhynchelmis (//o^- 



nella ; see Ann. d. Sc. Nat. 1844, II. p. 81, PI. I. II. meister, Ibid. 1843, 1, p. 192, Taf. IX. fig. 8). 



