116 



Eetractorens og Nervestrengens Overflade er besat med 

 disse Celler (Fig. 34 p', p', p'), der med deres lange 

 Cilier holde Blodlegemerne i en stadig Circulation, Hos 

 Ph. Lovénii, hvor Peritoneum er meget kjernerigt, viser 

 det ogsaa en fin Stribning, og hos Sipunculus priapuloi- 

 des indeholder det Muskelfibre. Disse ligge temmelig 

 spredte, men dog regelmæssigt og jevnt fordelte i to 

 Lag, hvis Fibre krydse hinanden under 45° (Fig. 4 A, f, f, 

 Fig. 4 B, f). 



Ved Fordøielseskanalen maa vi i det Væsentlige slutte 

 os til Graber, hvad det Histologiske betræffer, medens 

 vi have bibeholdt Ehlers og Kefersteins Inddeling i Spise- 

 rør, den egentlige Tarm og Kectum. Hos de to Sipun- 

 culus-Arter, der af os ere beskrevne, og som ere de 

 eneste hidtil kj endte i den skandinaviske Fauna, findes ikke 

 de af Ehlers og Keferstein omtalte blindsækformige, bu- 

 skede Organer, der skulle ligge i Nærheden af Analaab- 

 ningen, heller ikke den „Wimperfurche", der løber langs 

 Tarmens indvendige Flade hos Sipunculus nudus; der- 

 imod findes hos Sipunculus norvegicus, strax nedenfor 

 Anus paa hver Side af Kectum et lidet kjærtelformigt Or- 

 gan, der aabner sig i Endetarmen, ligesom vi have fun- 

 det hos S. norvegicus og S. priapuloides, samt paa en- 

 kelte Phascolosoma-Arter en liden Divertikel paa Rectum, 

 hvilken har været fyldt med det almindelige Tarmindhold. 



NERVESYSTEMET. 



Foruden det allerede ovenfor Omtalte og det ved 

 Ehlers og Kefersteins Undersøgelser Bekj endte, skulle vi 

 fremhæve, at paa O smiumspræp arater er saavel Bugstren- 

 gen, som dens Grene fint stribede, uden noget kornet 

 Udseende, ligeledes paa ganske friske, levende Exempla- 

 rer af Onchnesoma Steenstrupii. Der sees rigtignok fine 

 Korn paa Bugstrengen, saaledes som Keferstein angiver 

 det for Sipunculus nudus; men disse Korn tilhøre Celle- 

 laget, der omgiver selve Nervefibrene. Først naar Dyret 

 begynder at dø, bliver baade Bugstrengen og dens Grene 

 kornede. 



Hos Onchnesoma Steenstrupii, hvis ^Bugstreng i 

 Snabelen er overmaade tynd, og derfor let kan exami- 

 neres gjennem dens hele Tykkelse uden nogen særlig Præ- 

 paration, findes i Centrum af Nervestrengen talrige Grup- 

 per af Nerveceller langs hele Snabelen (Tab. 15, Fig. 

 35 a, a). Noget Lignende kunde ikke paavises hos andre 

 Arter. De finere^ Nerveforgreninger ere, paa Grund af 

 deres overordentlige Tyndhed, yderst vanskelige at følge 

 endog paa korte Strækninger hosPhascolosoma- og Onchne- 

 soma- Arter; imidlertid have vi dog forfulgt dem et 

 lidet Stykke, og de vise da omtrent et lignende ganglio- 

 nært Forhold med udstraalende Grene (Fig. 35 g), som vi 

 nu skulle omtale for Sipunculus's Vedkommende. Hos 

 unge Exemplarer af Sipunculus norvegicus, som ere be- 

 handlede med Osmiumsyre og senere farvede med Hæ- 



be clearly seen how the interior surface of the skin, as 

 well as the exterior surfaces of the alimentary canal 

 of the retractor and of the nervous cord are covered 

 with these cells (fig. 34 p', p', p') which with their long 

 cilia keep the blood-globules in a constant circulation. 

 In the Ph. Lovénii, where the peritoneum is very rich in 

 nuclei it exhibits also a fine striation; and in the Si- 

 punculus priapuloides it contains muscular fibres. These 

 are rather dispersed, but yet are regularly and evenly 

 distributed in two layers, the fibres of which cross each 

 other at an angle af 45° (fig. 4 A, f, f, fig. 4 B, f). 



As to the digestive canal, we must in all essential 

 points coincide with Graber in respect of the histology 

 while we have retained Ehlers and Kefersteins division 

 into oesophagus, the proper intestine and rectum. In 

 the two sorts of Sipunculus, which have been described 

 by us, and which are the only sorts hitherto known in 

 the Scandinavian Fauna, the cæca-like bushy organs 

 mentioned by Ehlers and Keferstein as situated in the 

 vicinity of the Anal aperture, are not found, nor the 

 "Wimperfurche" running along the interior surface of the 

 intestine, in the Sipunculus nudus; but we find in the 

 Sipunculus Norvegicus, immediately below the anus, on 

 each side of the rectum, a small gland-shaped organ 

 opening into the rectum; as likewise we have found in 

 S. Norvegicus and priapuloides, and in some species of 

 Phascolosoma, a small diverticle in the rectum filled with 

 the ordinary, contents of the intestine. 



THE NERVOUS SYSTEM. 



Besides what has been already previously mentioned, 

 and what is known from the researches of Ehlers and 

 Keferstein, we will point out that, in Osmium-prepara- 

 tions, the ventral cord and its branches are finely striated, 

 without any granulated appearance, as is the case also 

 in quite fresh living specimens of Onchnesoma Steenstrupii. 

 There are indeed to be seen some fine granules on the 

 ventral cord, as Keferstein states in reference to Sipun- 

 culus nudus; but these granules belong to the layer of 

 cells which surrounds the nervous fibres. Only when the 

 animal begins to die, the ventral cord and its branches 

 become granulated. 



In the Onchnesoma Steenstrupii, the ventral cord of 

 which is in the proboscis extremely thin, and therefore 

 may easily be examined in its whole substance without 

 any special preparation, there are found, in the centre 

 of the nervous cord, numerous groups of nervous cells 

 along the whole proboscis (Tab. 15, Rg. 35 a, a). Nothing 

 similar could be noticed in other species. The finer ramifi- 

 cations of the nerves are, by reason of their extraordinary 

 tenuity, extremely difficult to follow, even to short distances, 

 in the Phascolosoma and Onchnesoma species; however 

 we have traced them a little way; and so far they exhibit 

 a similar ganglionated construction with radiating branches 

 (ßg. 35 g), which we will now notice in reference to the 

 Sipunculus. In young specimens of Sipunculus Norvegicus, 

 treated with Osmium-acid and afterwards colored with 





