117 





matoxylin, er det derimod lettere at demonstrere. De 

 fra Bugstrengens primære Grene (Fig. 9 pn) udgaaende 

 Traade ere meget talrige og danne en Mængde Anasto- 

 moser (Fig. 9 nt, nt, nt). Fra Hovedstammen (den primære 

 Gren) udgaa regelmæssigt, i hvert Mellemrum imellem to 

 Bundter af Længdemuskler, 2 — 3 Grene paa hver Side. 

 Disse Grene anastomosere saavel indbyrdes, som med de 

 Grene, der komme fra den oven- og nedenfor liggende 

 Hoved-Stamme. Herved dannes paa Ringmusculaturen 

 temmelig regelmæssige, paalangs anastomoserende Nerve- 

 net, der ligge i Længdemusklernes Mellemrum. I dette 

 Net findes talrige ganglionære Knuder (Fig. 9 g, g, g), 

 hvorfra udgaa Grene, dels til Ring- og Længdemusklerne 

 (Fig. 9 f, f), dels gjennem Ringmuskellaget til Hud- 

 legemerne (Fig. 9 n, n), og endelig findes Grene, der tabe 

 sig paa eller i Epithelets Celler (Fig. 9 a). 



KARSYSTEMET. 



Dette har været Gjenstand for en Mængde Naturfor- 

 skeres Undersøgelser, og om end Resultatet af disse i 

 enkelte Punkter kan 'være noget afvigende, saa stemme 

 dog Alle overens deri, at der ialmindelighed findes hos 

 Sipunclerne to contractile Kar langs Spiserøret, hvilke 

 foroven danne en Ringkanal, der corresponderer med 

 Hulheden i Tentaklerne, imedens der hos Phascolosoma- 

 erne i Regelen kun findes et saadant contractilt Kar. Med 

 Hensyn til dette Karsystems Function, saa have Menin- 

 gerne været forskj eilige. Nogle have antaget det for at 

 staa i Aandedrættets Tjeneste, Andre i den almindelige 

 Blodcirculations, imedens Brandt og med ham enkelte 

 tidligere Forskere have ment, at det udelukkende tjener 

 som mechanisk Kraft for Tentaklernes Udstrækning. De 

 der antage, at Tentakularkarsystemet er et Respirations- 

 og Circulationsapparat, formene, at der mellem dette og 

 Kropshulheden maa være en umiddelbar Forbindelse, 

 som de dog ingenlunde have paavist; de Andre paastaa, 

 at ingen saadan Forbindelse existerer, og at følgelig Ten- 

 taklernes Kar med de contractile Kanaler udgjøre et for 

 sig afsluttet System; og til denne Mening maa vi slutte 

 os. Se vi hen til Slægten Petalostoma, der kun har to 

 Tentakler, og til vore to nye Slægter Onchnesoma og Ty- 

 losoma, der aldeles ingen Tentakler have og heller ikke 

 ere i Besiddelse af noget Karsystem; men at der ikke- 

 destomindre hos disse Dyr, ligesaa godt som hos de 

 øvrige Sipunculider med fuldt udviklet Tentakularsystem, 

 foregaar et Slags Aandedræt, — saa forekommer det 

 os, at det her omtalte Karsystem intet har med Respira- 

 tionen at gjøre; men at det svarer, hvad allerede ældre 

 Forskere have gjort opmærksom paa, til Holothuridernes 

 Vandkarsystem. Hos vore to Sipunculus-Arter have vi i 

 Huden iagttaget Længdekar, der i enkelte Henseender have 

 noget tilfælles med de af Semper omtalte. Disse Hudkar 

 dannes derved, at den Hinde, vi have kaldt Peritoneum, 

 gjør Udkrængninger, som trænge ind imellem Muskelhu- 

 den og Epithellaget i Form af runde Kar, der fortil, 



Hæmatoxyline, it is however much more easy to demon- 

 strate. The filaments, issuing from the primitive branches 

 of the ventral cord (fig. 9 pn), are very numerous, and 

 form a multitude of anastomoses (fig. 9 nt, nt, nt). From 

 the main trunk (the primitive branch) there issue regu- 

 larly in each interval between two fascicles of longitudinal 

 muscles, 2 — 3 branches on each side. These branches 

 anastomose with each other and with the branches that 

 come from the main trunk situated above and below. 

 Hereby there are formed, on the annular muscles, rather 

 regular longitudinally anastomosing nerve-nets, which lie 

 in the intervals of the longitudinal muscles. In these 

 nets we find numerous] ganglionic knots (fig. 9 g, g, g), 

 from which there issue branches, partly to the annular 

 and longitudinal muscles (fig. 9 f, f), partly through the 

 layer of annular muscle to the cuticular bodies (fig. 9 n, n), 

 and finally there are branches which accumulate on or 

 in the cells of the epithelium (fig. 9 a). 



THE VASCULAR SYSTEM. 



This has been the subject of the investigations of a 

 number of natural historians; and even if the result of 

 these researches may be in some points a little divergent, 

 yet they all agree in shewing that there are generally in 

 the Sipunculi two contractile vessels along the oesopha- 

 gus, forming above an annular canal which corresponds 

 with the cavity in the tentacles; while in the Phascolo- 

 somas there is usually only one such contractile vessel. 

 With respect to the function of this vascular system, 

 opinions have been divided. Some have regarded it as 

 standing in the service of the respiration ; others, in that 

 of the general blood-circulation; while Brandt, and 

 with him a few of the earlier naturalists, have been of 

 opinion that it serves exclusively as a mechanical power 

 for the extension of the tentacles. Those who assume 

 that the tentacular-vascular system is an apparatus of 

 respiration and circulation, hold that there must be be- 

 tween it and the perivisceral cavity a direct connexion, 

 which however they have in no wise demonstrated; the 

 others maintain that no such connexion exists, and that 

 consequently the vessels of the tentacles with the con- 

 tractile canals form a complete system for themselves; 

 and we must coincide with this opinion. If we look to 

 the genus Petalostoma, which only has two tentacles, and 

 to our two new genera Onchnesoma and Tylosoma, which 

 have no tentacles at all, nor possess any vascular system, 

 and consider that in these animals, as well as in the 

 other Sipunculidæ with a fully developed tentacular system, 

 a sort of respiration does take place, it appears to us 

 that the vascular system here noticed has nothing to do 

 with the respiration, but that it answers, as earlier natura- 

 lists have already remarked, to the water-vessel system 

 of the Holothuridæ. In our two species of Sipunculus 

 we have observed in the skin longitudinal vessels, which 

 in certain respects have something in common with those 

 mentioned by Semper. These cuticular vessels are formed 

 by the membrane, which we have called peritoneum, in- 



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