125 



lille Blindsæk aabner sig i Tarmen, og Indholdet var det 

 samme som dennes, nemlig lerholdig Sand, hvori enkelte 

 Rhizopoder fandtes. Et Stykke ovenfor Analaabningen 

 udgaar fra en Længdemuskel en fin Muskeltraad (Spin- 

 delmuskel), der slaar sig over Rectum, fæster sig paa 

 Divertikelen og gaar derfra ned imellem Tarmslyngnin- 

 gerne, hvor den forsvinder. De to knippeformige Blind- 

 sække, som findes paa Sipunculus nudus, ganske i Nær- 

 lieden af anus, have vi ikke seet paa denne Art. Langs 

 Spiserøret findes de to lange, contractile Kar, der tilhøre 

 Tentakularsystemet. 



To Segmentalorganer, der ere omtr. 8 Mm. lange, 

 iemmelig småle og meget contractile, hvorved de antage 

 en forskj eilig Form, Fyldte ere de saagodtsom vandklare; 

 i contractu Tilstand blive de mindre gjennemsigtige. 



Langs Dyrets Bugflade sees en temmelig tyk Nerve- 

 streng, som svulmer lidt kølleformigt op mod den bagerste 

 Ende. Hvor Nervestrengen ligger tæt til Bugvæggen, af- 

 giver den regelmæssigt et Par Grene til hver Ringmuskel ; 

 hvor den viger fra Bugvæggen for at stige mod Spiserø- 

 ret, afgiver den mange tykke, lange, temmelig løstliggende 

 Grene til dette (Fig. 8 nn), ligesom den, idet den løber 

 imellem de to Retractorer, afgiver en Gren til hver. Hvor 

 Nervestrengen begynder at forlade Bugvæggen, er den 

 fæstet til denne ved en Muskel, der gaar fortil mod Ten- 

 takelkrandsen. Foruden til Ringmusklerne, sender Ner- 

 vestrengen Grene til Huden. Saavel Kropshulheden, som 

 de i den placerede Organer ere beklædte af Peritoneum. 





Det i Kropshulheden indeholdte Fluidum er næsten vand- 

 klart, svagt rosenrødt, og deri findes de for Sipunclerne 

 almindelige Celler og krukkeformige Legemer. 



Sipunculus norvegicus er funden i Hardangerfj orden 

 indtil 250 Favne og i Bergensfjorden paa 150 Favnes 

 Dyb, blød, lidt sandholdig Lerbund. Den characteriseres 

 saaledes: 



Kroppen 44 Mm. lang, 20 Mm. i Omkreds, cylindrisk, 

 vandklar, dens bagerste Del omgiven af en fremspringende 

 Vold. Trende Muskellag, hvoraf det indre, Længdemusk* 

 lerne 24, — det mellemste, Skraamusklerne 12, — og det 

 yderste, Ringmusklerne omtrent 100. Snabelen kort, omtr. 

 V 4 af Kroppens Længde, besat med coniske Papiller. Ten- 

 takelmembranen 8-fliget, lappet. 



FORKLARING OVER FIGURERNE. 



Tab. 13. Fig. 7. Sipunculus norvegicus, naturlig Størrelse. 



.Fig. 8. Samme forstørret; aabnet. p Snabelen; s, s Segmental- 

 organer; n den opsvulmede nederste Del af Nervestren- 

 gen; nn Nervegrene; sp Spindelmuskel; d Divertikel; 

 r,r Retractorer; re Rectum; m, m Muskelstrenge til Tar- 

 men; Im Længdemuskler; ta Tarmslyngningerne; t Ten- 

 takler» 



where the intestine becomes smaller (rectum) there is an 

 almost pear-shaped diverticle of 1 Mm. length. This 

 little cæcum opens into the intestine and the contents 

 are nearly the same, namely clayey sand, wherein a few 

 Rhizopods have been found. A little way above the anal 

 aperture, there issues, from a longitudinal muscle, a fine 

 muscular fibre (the fusiform muscle) which extends over 

 the rectum, attaching itself, on the diverticle, and thence 

 descends] between the circumvolutions of the intestine, 

 where it disappears. The two fascicular cæca, which are 

 found in the Sipunculus nudus quite in the vicinity of 

 the anus, we have not been able to discover in this 

 species. Along the oesophagus there are two long con- 

 tractile vessels, which belong to the tentacular system. 



There are two segmental organs about 8 Mm. long, 

 rather narrow and very contractile, whereby they acquire 

 a different form. When full they are almost pellucid; 

 but when in a contractile state, they are less transparent. 



Along the ventral surface of the animal, there appears 

 a rather thick nervous cord, which swells, a little club- 

 like, towards the posterior extremity. Where the ner- 

 vous cord lies close to the ventral surface, it throws out 

 regularly a pair of branches to each annular muscle: 

 where it recedes from the ventral surface, rising towards 

 the oesophagus, it throws out many thick, long, rather 

 loose-lying branches to the latter (fig, 8 nn); as also while it 

 runs between the two retractors, it furnishes a branch 

 to each. Where the nervous cord begins to leave the 

 ventral surface, it is attached to the same by a muscle, 

 which is fixed in the direction of the tentacular circlet. 

 Besides sending branches to the annular muscles, the 

 nervous cord sends out also branches to the skin. The 

 perivisceral cavity, as well as the organs situated therein, 

 are covered by the peritoneum. 



The fluid contained in the perivisceral cavity is nearly 

 pellucid, slightly rose-colored, and is composed of the 

 usual cells and pot-shaped bodies common to the Sipunculi. 



Sipunculus norvegicus has been found in the Har- 

 dangerfj ord at a depth of 250 fathoms, and in the Bergens- 

 fjord in 150 fathoms, on soft rather sandy clay bottom; 

 rare. It is thus characterised : 



The body 44 Mm. long, 20 Mm, in circumference, 

 cylindrical, pellucid; its posterior part surrounded by a 

 prominent — ridge (annular projection). Three layers 

 of muscles'; the interior, longitudinal muscles 24, — the 

 middle oblique muscles 12, — and the exterior, the annular 

 muscles, about 100 in number. The proboscis short, 

 about V 4 of the length of the body, covered with conical 

 papillæ. The tentacular membrane lobed, 8 lobes. 



EXPLANATION OF THE FIGURES. 



Tab. 13, fig. 7. Sipunculus norvegicus natural size. 



Fig. 8. The same magnified, opened, p the proboscis; s, s seg- 

 mental organs; n the swollen lower part of the nervous 

 cord; nn nerve branches; sp fusiform muscle; d diver- 

 ticle; r,r retractor; re rectum; m, m muscular appen- 

 dage to the intestine; Im longitudinal muscles; ta cir- 

 cumvolutions of the intestine; t tentacles. 



17 



