25 



Blodkarsystemet. 



Hjertet (Fig. 1, Fig. 2, c) er af langstrakt spindel- 

 dannet Form og strækker sig, umiddelbart ovenfor 

 Tarmen, igjennem hele Midtkroppen og Størsteparten 

 af Bagkroppen, endende omtrent ved Enden af den- 

 nes 3die Segment. I Midtkroppens 5te Segment har 

 det sin største Vidde og viser her til hver Side en 

 meget iøinefaldende Tværspalte. En lignende, men 

 betydelig mindre Spaltaabning sees til hver Side 

 helt fortil, ved Hjertets Begyndelse. Claus har 

 desuden afbildet, mellem begge Par, 4 meget smaa 

 dorsale Spaltaabninger, som det dog ikke er lykkets 

 mig at faa se tj'deligt. Fra Hjertets forreste Ende 

 udgaar en, ialfald i sit inderste Parti tydelig Arterie, 

 og ogsaa Hjertets bagre Ende har forekommet mig 

 at fortsætte sig i en lignende bagudlobende Arterie. 

 Noget virkeligt udviklet Blodkarsystem synes dog 

 neppe at være tilstede, og Blodet circulerer, som 

 hos andre lavere Crnstaceer, væsentlig kun i væg- 

 løse Huln^m mellem Bindevævet og Musklerne. 

 I Branchialfodderne er allerede omtalt Tilstedevæ- 

 relsen af saadanne med hinanden anastomoserende 

 Blodgange, navnlig i de 2 ydre Vedhæng (Exopodit 

 og Epipodit). Et lignende System af vægløse Blod- 

 kanaler findes ogsaa mellem Rygskjoldets 2 Lamel- 

 ler, og da Cirkulationen her er meget livlig, har 

 man Grund til at antage, at Rygskjoldet spiller en 

 ikke uvæsentlig Rolle ved Dyrets Respiration. 



Nervesystemet 



At undersoge Nervesystemet i sine Detailler, 

 er forbundet med særdeles store Vanskeligheder, da 

 dets Centraldele ligger saa tæt omgivne af Muskler 

 og Bindevæv, at de yderst vanskeligt lader sig 

 isolere ved Disection. Paa Tværsnit af Kroppen 

 (Pl. V, Fig. 2) kan man dog let orientere sig angaaende 

 Buggangliekjædens Beliggenhed (g), og kan herefter 

 bestemme dens Plads ogsaa i Profil af Dyret (se 

 Fig. 1). Hjernegangliet har det kun lykkets mig 

 at se temmelig ufuldstændigt. Det synes ikke at 

 være af nogen betydelig Storrelse, og udsender, for- 

 uden Synsnerverne, stærke Nervestammer til de 

 2 Par Følere. I Midtkroppen ligger de enkelte 

 Knuder af Buggangliekjæden tæt sammen, kun for- 

 bundne med meget korte og tykke Længdecommis- 

 surer, mellem hvilke der knapt er noget Mellemrum. 

 Selve Ganglierne er forholdsvis smaa og alle af ens 

 Størrelse, deres 2 Halvdele fuldkommen sammen- 



i — G. 0. Sårs: Fauna Norveriiæ. 



(cd, cv), grouped nearly in the form of a rosette, 

 around and close in to the intestine, with a somewhat 

 largish interval between the dorsal pair. 



The blood-vessel system. 



The heart (fig. 1, fig. 2 c) is of elongate, fusi- 

 form shape, and extends, immediately above the 

 intestine, through the entire mesosome and the 

 greater part of the metasome, terminating at about 

 the extremity of the 3rd segment of the latter. 

 It has its greatest breadth in the 5th segment of 

 the mesosome, and exhibits here on either side a 

 very prominent transversal fissure. A similar, but 

 considerably smaller fissure-aperture is seen on eacli 

 side, quite in front, at the commencement of the 

 heart. Claus has illustrated besides, between both 

 pairs, 4 very small dorsal fissure-apertures, which 

 I have, however, not been fortunate enough to ob- 

 serve distinctly. From the foremost extremity of 

 the heart there issues a, at least in its innermost 

 portion, distinct artery; and also the posterior ex- 

 tremity of the heart has appeared, to me, to con- 

 tinue itself in a similar backward running artery. 

 Any real, developed blood-vessel .system scarcely 

 appears, however, to be present; and the blood 

 circulates, as in other lower Crustaceans, princi- 

 pally, only in cavities, without walls, between the 

 connective-tissue and the muscles. In the branchial 

 feet, the presence of such blood pasages, anastom- 

 osing with each other, has already been mentioned; 

 especially in the 2 outer appendages (exopodite and 

 epipodite). A similar system of blood-ducts, without 

 walls, is also found between the 2 lamellæ of the 

 carapace, and as the circulation is here very active 

 there is reason to suppose that the carapace plays 

 a not unimportant part in the respiration of the 

 animal. 



The nervous system- 



To investigate the nervoi^s system in its details 

 is a matter of particularly great difficulty, as its 

 central portions lie so closely surrounded by muscles 

 and connective tissue that it is excessively difficult 

 to isolate them by dissection. In transversal sec- 

 tions of the body (PI. V, fig. 2) we can, however, easily 

 obtain information concerning the situation of the 

 ventral ganglial chain (g), and can from this deter- 

 mine its situation also in a side-view of the animal 

 (see fig. 1). I have not been fortunate enough to 

 observe the ganglion of the brain very perfectly. It 

 does not appear to be of any considerable size, and 

 sends ofi", besides the optical nerves, powerful ner- 

 vous stems to the 2 pairs of antennæ. In the meso- 

 some, the individual knots of the ventral ganglial 

 chain lie close together, only connected by very 

 short and thick longitudinal commissures, between 

 which there is scarcely any interval. The ganglia. 



