51 



Buggangliekjæden (se Fig. 1) er ikke vanskelig 

 at observere saavel hos levende Exemplarer som 

 hos Specimina opbevarede i fortyndet Spiritus. Man 

 hehover blot med Forsigtighed at ndbrede Branchial- 

 fodderne til hver Side og indstille Mikroskopet skarpt 

 paa Bngfladen af Dyret, og denne Del af Nerve- 

 systemet vil, ialfald delvis, klart og tydeligt sees, 

 uden at nogen virkelig Dissection er fornøden. Dog 

 er dens forreste Del altid temmelig vanskelig at ob- 

 servere, da den fordetmeste skjules af de lidet gjen- 

 nemsigtige Kindbakker og af Kjæverne. Buggang- 

 liekjædeji viser en meget udpræget stigedannet Form, 

 idet den bestaar af 2 vidt adskilte stærke Nerve- 

 stammer, som i hvert Segment forbindes med en 

 dobbelt Tværcommissur. Paa dette Sted viser hver 

 Nervestamme en temmelig svag ganglios Opsvulm- 

 ning (se Fig. 5), fra hvis ydre Side 2 stærke Nerver 

 iidspringer. Det ene Par af disse Nerver trænger 

 ind i de respective Branchialfodder, medens det 

 andet Par synes at innervere de Muskler, der fra 

 Kroppen passerer til Basis af disse Lemmer. En 

 anden betydelig svagere Nerve udspringer omtrent 

 fra Midten af enhver af Længdecommissurerne og 

 synes at ende i Legemets Sidemuskler. Antallet af 

 de Nerveknuder, der sammen med Commissurerne 

 danner Buggangliekjæden, er paa hver Side 15 (se 

 Fig. 1). Heraf er de 3 forreste Par bestemte for 

 Kindbakkerne og de 2 Par Kjæver, det bågeste Par 

 for Genitalsegraentet, de 11 ovrige for de 11 Par 

 Branchialfodder. Buggangliekjæden er saaledes ind- 

 skrænket til Forkropjjen alene. I Bagkroppen fort- 

 sættes rigtignok de 2 Nervestammer lige til Enden 

 af sidste Segment, men uden her at være forbundne 

 ved Tværcommissurer og uden at danne tydelige 

 Ganglier. I hvert Halesegment ndsender disse Nerve- 

 stammer line Nervegrene, hvoraf nogle sj-nes at ud- 

 Itrede sig i Halens Muskulatur, medens andre ender 

 med en liden ganglios Opsvulmning lige under Huden 

 (se Fig. 8). Paa disse Steder sees altid en over- 

 ordentlig fin Børste (Foleborste) at springe frem, til- 

 dels omgiven af smaa Hudpapiller (Fig. 9). 



Angaaende den Maade, hvorpaa de ovrige Ner- 

 ver ender, skal her blot omtales Forholdet med de 

 til Iste Par Folere gaaende Nerver og Synsnerverne. 



Forste Par Foleres Nerver ud.springer (se Fig. 4) 

 tilsyneladende fra det basale Parti af Synsnerverne, 

 idet begge Nerver ved sit Udspring er omgivet af 

 en fælles Nerveskede. De træder deretter til hver 

 Side som en tynd Stamme ind i Iste Par Foleres 

 Basis og fortsætter sig igjennem deres Axe indtil 

 henimod Spidsen. Her deler Nerven sig (se Fig 2) 

 i 2 Grene, der tilsammen danner en betydelig gang- 

 lios Masse ved Spidsen af Foleren. Fra denne 



The ventral ganglion chain (see fig. 1) is not 

 difficult to examine, either in living specimens or in 

 those preserved in diluted spii'it. It is only neces- 

 sary to turn the branchial legs carefully to either 

 side, and adjust the microscope close to the animal's 

 ventral surface, when this part of the nervous sys- 

 tem, will, at any rate to some extent, be seen 

 clearly and distinctly, without the necessity of 

 actual dissection. The front part, however, is always 

 rather difficult of observation, as it is generally 

 almost hidden by the but slightly transparent man- 

 dibles and by the maxillæ. The ventral ganglion 

 chain exhibits a marked ladder-like form, in that it 

 consists of 2 strong, widely-separated nerve-stems, 

 which are connected in each segment by a double 

 transverse commissure. Here each nerve-stem exhi- 

 bits a rather sliglit ganglionic dilatation (see fig. 5), 

 on the outer side of which, 2 strong nerves have 

 their origin. One of these pairs of nerves penetrates 

 into the respective branchial legs, while the other 

 pair appears to innerve the muscles pas.sing from 

 the body to the base of those appendages. Another 

 much weaker nerve has its origin almost in the 

 middle of each of the longitudinal commissures, and 

 appears to end in the lateral muscles of the body. 

 The number of ganglia that, together with the com- 

 missures, form the ventral ganglion chain, is 15 on 

 each side (see fig. 1). Of these the 3 foremost pairs 

 are destined for the mandibles and the two pairs of 

 maxillæ, the hindmost pair for the genital segment, 

 and the remaining 11 for the 11 pairs of branchial 

 legs. The ventral ganglion chain is thus confined to 

 the anterior division of the body. It is true that 

 the 2 nerve-stems are continued imthe hinder part of 

 the body as far as the end of the last segment, but 

 without being there connected by any transverse 

 commissures, and without forming distinct ganglia. 

 In every caudal segment these nerve-stems send out 

 delicate rami, some of which appear to spread over 

 the caudal musculature, while others end in a little 

 ganglionic ti^berosity just below the integument (see 

 fig. 8.) At these places an exceedingly fine bristle 

 (sensory bristle) is always seen to protrude, parti- 

 ally surrounded by small cutaneous papillæ (fig. 9). 

 With regard to the manner in which the re- 

 maining nerves end, only the circumstances relating 

 to those of the 1st pair of antennæ, and the optic 

 nerves will be mentioned here. 



The nerves of the 1st pair of antennæ (see fig. 4) 

 apparently originate from the basal part of the 

 optic nerves, lioth nerves being surrounded at their 

 origin by a common neural-sheath. The}' then pass 

 to either side in the form of a thin stem into the 

 base of the first pair of antennæ, whence they con- 

 tinue along the axis of the latter almost to the 

 extremity. Here the nerve divides (see fig. 2) into 

 2 branches, which to^'ether form a considerable 



