^331. 



THE INSECIA. 



41^ 



(Nervus recurrens) which passes over the oesophagus to the stomach, giv- 

 ing ofi" branches right and left. Reaching the stomach, it divides, after 

 having formed a ganglionic enlargement, into two principal branches. 



The double Stomato-gastric nerve consists of one, two, or three pairs of 

 small ganglia, situated behind the brain, on each side of the oesophagus, 

 and communicating with each other, with the posterior extremity of the 

 brain, and with the Nervus recurrens, by delicate filaments. These fila- 

 ments send fine threads to the oesophagus, and, at certain points, anastomose 

 with the single nerves.'^* 



With the Hemiptera, a single Splanchnic nerve hns been observed, and, 

 for the double system, there has been seen, on each side of the oesophagus, 

 two small ganglia, one behind the other.'-* 



With the Diptera, the splanchnic system appears to be present ; at least, 

 there has been observed on the Chyliferous stomach of the Hippoboscidae, 

 a pair of filaments belonging, probably, to the double system.'"' 



The Lepidoptera have a highly-developed Nervus recurrens, which often 

 forms, with the caterpillars, several small ganglia lying behind each other 

 on each side of the brain, and connected together by a double nervous 

 arch. The double system arises on each side of the oesophagus, from two 

 ganglia, situated one behind the other, which, with the caterpillars and 

 pupae, are often approximated to a blending together, and which send off, 

 beside the filaments anastomosing with the recurrent nerve, threads to the 

 dorsal vessel.''" T^ie Hymenoptcra,'^' Neuroptera, and Orthoptera, also, 

 have the two kinds of splanchnic systems. The double trunks are highly 

 developed with the Acrididae, and the Gryllotalpida, and have two pairs 

 of ganglia at their upper extremity, beside one or two on their course ; 

 while, with the Libellulidae, Blattidae, and especially the Phasmidae, the 

 single nerve is the most developed.''^' 



1 For the Splanchnic ner^^ous system of the In- 

 secta, of which Swammerdamm had already ol)- 

 Berved the recurrent nerve, see, beside the gene- 

 ral works of Burmeister (Ilandb. &c. I. p. 308), 

 and Lacordnire (Introduct. &c. II. p. 214), espe- 

 cially J. Müller, Nov. Act. Acad. Nat. Cur. XIV. 

 1828, p. 73 ; Brandt (Isis, 1831, p. 1103, also his 

 Bemerk, über die Mundmagen-oder Einfieweidener- 

 ven d. Evertebr. 1835, p. 16, or Ann. d. Sc. Nat. 

 V. 1836, p. 95), and Newport, Cyclop. &c. loc. 

 cit. II. p. 957). 



2 Meckel (Beitr. zur vergleich. Anat. I. p. 4) 

 has observed the Iferviix recurrens in the com- 

 mon Cicada, and Brandt (Bemerk. &c. p. 23, Taf. 

 II. fig. 1, 2) has observed the same with Lygaeus, 

 and at the same time the ganglia of the double 

 system. 



3SeeZ>. Dufour, Ann.d. Sc Nat. III. 1845, p. 67. 



i The recurrent nerve was first discovered in the 

 silk-worm by S ivammerdamm (Bib. der Nat. p. 

 132, Taf. XXVIII. fig. 3, g.). Subsequently, Ly- 

 onet (Traite, &c., p. 577, PI. XII. fig. 1, PI. XIII. 

 fig. 1, PI. XVI. fig. 14, PI. XVIII. fig. 1) de- 

 scribed with the larva of the Goat-moth, the 

 double system and its relations with the dorsal 

 vessel. Since then, the two systems have been ob- 

 served in the larvae, pupae, and imagines of various 

 Lepidoptera; see SucA-ow (Anatom, physlol. Unter- 

 such. 40, Taf. VII. fig. 33-38, (pupa and imago of 

 Gastropacha pini)), who has described the double 

 system and the cardiac nerve. See, also, J. Mid- 

 ler (Nov. Act. Nat. Cur. loc. cit. p. 97 (the recur- 

 rent nerve of a larva of Sphinx)), and Brandt 

 (Isis, lue. cit. p. 1104, Taf. VII. fig. 3, 4, and Be- 

 merk, kc. p. 20), who has described the two sys- 



35* 



tems with the imago and larva of Bombyx mnri. 

 The works of Newport (Philos. Trans. 1832, p. 

 383, PI. XII. XIII., and 1834, p. 389, PI. XIII. 

 XIV.) on the larva and imago of Sphinx ligustri, 

 are very distinguished. 



.5 See Treviranus (Verm. Schrift. III. p. 59), 

 who thinks he has observed the Nervus recur- 

 rens with Apis mellifica ; Brandt, also (Medizin. 

 Zool. II. p. 203, Taf. XXV. fig. 32, and his Be- 

 merk. &c. p. 22), has described the two systems in 

 this species, and in the Bumble-bee (Apis terres- 

 tris). 



G According to Burmeister (Handb. &c. I. p. 

 310, Taf. XVI. fig. 6 {Gryllns misrratnrius)), the 

 recurrent nerve leaving the frontal ganglion, runs 

 backwards and ends, after a short course, in a 

 ganglion which connects by two filaments with the 

 internal ganglia of the double system. These 

 last send off several branches to tlie oesophagus, 

 and connect, through two filaments, with the exter- 

 nal ganglia of the same system. From these exter- 

 nal ganglia arise two lateral trunks which run 

 along the oesophagus and are distributed to the 

 gizzard, foi-ming a nervous plexus having four 

 ganglia. See, also, for the same species, Brandt, 

 in the Isis, 1831, p. 1104, Taf. VII. fig. 5. Accord- 

 ing to this last author (Bemerk. &c. p. 29, Taf. II. 

 fig. 7-9), the double system of Gryllotalpa is sim- 

 ilarly disposed, only the nervous |)lexu3 of the giz- 

 zard arises from two posterior ganglia of the two 

 trunks. See, also, for that of Gryllotalpa, L. 

 Dufour, Recherch. sur les Orthopt. &c. p. 285, 

 Pl.III. fig. 22. With Phasma ferula, the four 

 anterior ganglia of the single system are small, but. 

 for compensation, the double system is very com-. 



