^ 302. THE ARACHNOIDAE. S'fS 



§ 302. 



A Splanchnic nervous system has been observed with only the higher 

 Arachnoidae ; but here it is highly developed. The odd stomachic nerve 

 has been the part most difficult to discover ; it is observed, however, with 

 some Araneae, — the posterior border of the brain sending off two small 

 filaments which traverse the central opening of the stomach but unite on 

 its dorsal surface.*" The Scorpionidae have a similar stomachic nerve which 

 also arises from the brain by two filaments which have a small ganglion at 

 the point of their union.'-'* 



With the Phalangidae, Araneae, Galeodea, and Phrynidae, the splanch- 

 nic nerves are very distinct. They arise from the posterior border of the 

 ventral nervous mass situated in the cephalothorax, and are distributed to 

 the digestive, respiratory, circulatory, and genital organs, and have, some- 

 times, ganglia on their course. With Phalangium, there are three of 

 these nerves ai'ising from the posterior border of the transverse portion of 

 the ventral mass. The middle one of these nerves divides into two 

 branches, which dilate into two ganglia connected together by a transverse 

 anastomosis. From these two ganglia arises a nervous plexus, which is dis- 

 tributed to the internal genital organs, and to the corium. The lateral 

 nerves, directly after their origin, likewise divide into two branches, each of 

 which forms a ganglion ; the external nerves after a shorter, and the inter- 

 nal after a longer course. The two external ganglia thus formed send fila- 

 ments to the terminal portion of the genital organs, while those of the two 

 internal ganglia are distributed to the digestive tube and neighboring or- 

 gans. '^> With the Araneae, the Galeodea, and Phrynidae, the posterior 

 ■extremity of the principal ventral ganglion sends off two considerable 

 nervous cords, contiguous, which pass into the abdominal cavity where they 

 are distributed, radiatingly, to the digestive organs, to the pulmonary sacs, 

 to the genital organs, and to other abdominal viscera. Sometimes, before 

 dividing, they unite in a common ganglion,'^* 



1 This Nervus sympathicus recurrens was (lis- IV. fig. 24, and Tulk, loc. cit. p. 325, PI. V. flg. 



covered l)y Brandt, with Epeira ; see Mediz. Zool. 31, 33. 



II. p. 90, Taf. XV. fig. 4, d., and fig. 6, c, or in -4 This ganglion has been observed by Trevira- 



the Isis, 1831, p. 1105, Taf. VII. fig. 6, b., and Be- nus (Bau d. Arach. p. 45, Taf. V. fig. 45), with the 



merk. üb. d. Muudmagennerven, loc. cit. p. 15, or indigenous Araneae, and by Dugis (Ann. d. Sc. 



Ann. d. Sc. Nat. V. p. 94, and XIII. p. 185, PI. Nat. VI. p. 175), with My^ale. According to 



IV. fig. 2, c. This same nerve has lieen refouiid by Brandt (Mediz. Zool. II. Taf. XV. fig. 3, and 



Grube (loc. cit. p. 302), with other indigenous Ann. d. Se. Nat. XIII. p. 185, PI. IV. fig. 4), this 



Araneae. With Mi/g'a/e, according to £)ks-^s (Ann. ganglion is wanting with Epeira, and Trevi- 



A. Sc. Nat. VI. p. 175), there are, instead cf two ranus (Zeitsch. f. Physiol. IV. p. 95), has vainly 



fiiinple filaments, two lateral ganglionic net-works, sought for it in a Brazilian spider. Blanchard 



from the brain to the stomach. (loc. cit. p. 1384), has found it with Galeodes, and 



^ See Newport, loc. cit.* fan der Hoeven (Tijdsch. X. p. 370), with Thely- 



3 See Treviranus, Verm. Sclirift. I. p. 38, Taf. phonus. 



* [ § 302, note 2.] See also Dufour, loc. cit. p. 251. —Ed. 



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