142 



ONGENESOMA STEENSTRUPII, Nobis. 

 (Tab. 15, Fig. 28—36). 

 Sipunculus pyriformis, Danielssen. 

 Yidenskabsselskabets Forhandlinger i Christiania, Aaret 1859, 

 V%g. 251. 



Phascolosoma pusillum, M. Sars. 

 Videnskabsselskabets Forhandlinger, Aaret 1868, benævnt, men 

 ikke beskrevet. 



Sipunculus aus Kilmore? Claparéde. 

 Müllers Archiv f. Anatomie u. Physiologie, Jahrgangl861, P. 540. 



Kroppen, 3 Mm. lang, 2 Mm. tyk, er pæreformig, 

 overalt besat med smaa coniske Papiller (Tab. 15, Fig. 

 30 p), ender bagtil i en liden Spids, og viser under stærk 

 Loupeforstørrelse et netformigt Udseende. Snabelen er 

 yderst tynd og lang, i fuldkommen udstrakt Tilstand indtil 

 34 Mm., besat med meget fine Papiller, der ere stillede 

 i regelmæssige Tverrækker og ophøre ganske omtr. 2 Mm. 

 fra Mundaabningen. Denne er rund og forsynet med 

 meget smaa bløde Fremstaaenheder (Fig. 30' o), der dan- 

 nes af Cylinderepithelet, som beklæder den indre Flade 

 af Spiserøret; der er forresten ingen Tentakler. Huden 

 er temmelig fast, og, naar Snabelen er udstrakt, saameget 

 gjennemsigtig, at de indre Organer kunne sees, men dog 

 meget utydeligt; dens indre Flade beklædt med det for 

 Phascolosomaerne almindelige Lag af sammenhængende 

 Ring- og Længdemuskler, hvilke ere meget tynde. Epithel- 

 laget dannes af meget store Celler, der indeholde foruden 

 Kjerner en Mængde grønligt Pigment (Fig. 33), der giver 

 Huden sin særegne fine grønlige Farve. Kun én Re- 

 tractor, der tager sit Udspring fra Kropshulhedens ba- 

 gerste Ende med en bred Grunddel, og gaar saa i Midten 

 af Legemet og Snabelen som en rund Søile lige hen til 

 Mundaabningen, omkring hvilken den fæster sig (Fig. 30 

 r, r, r, r). Spiserøret, der er meget langt og smalt, følger 

 Retractor et Stykke ned i Kropshulheden (Fig. 30 sp, 

 sp, sp), hvor det da gaar over i Tarmen (Fig. 30 t, t), 

 der danne r en Mængde løse Slyngninger paa venstre Side 

 af Retractor, hvilke gaa næsten henimod den bagerste 

 Ende; herfra gaar den igjen et langt Stykke forover, bøier 

 saa bagover for atter at gaa fortil over Retractor og kom- 

 mer nu paa høire Side af denne (Fig. 30 t 1 ), hvor den 

 danner dels enkelte Bugtninger, der ved fine Traade ere 

 fæstede til Kropshulheden, dels spiralförmige Slyngninger 

 (Fig. 30 t 2 ), der endelig gaa over i en lang, næsten lige 

 Endetarm, der munder ud paa Snabelen lidt ovenfor den- 

 nes Grunddel (Fig. 30 re, re). Segmentalorganet danner 

 en langstrakt, klar Blære, hvis frithængende Ende er co- 

 nisk tilspidset (Fig. 30 s). I Kropshulheden findes hyp- 

 pig en Mængde løse Æg. Nervestrengen tager sin Be- 

 gyndelse ved Retractorens Basaldel, løber langs Kroppens 

 og Snabelens indre Flade mod Spiserørets forreste Ende, 

 hvor den, som hos Sipunculiderne i Almindelighed, danner 

 en Ring (Fig. 30 n, n, n). Kropshulheden og samtlige deri 

 indeholdte Organer ere beklædte med Peritoneum. 



ONCENESOMA STEENSTRUPII, Nobis. 

 (Tab. 15, fig. 28-36.) 

 Sipunculus pyriformis, Danielssen. 

 Videnskabsselskabets Forhandlinger i Christiania, Aaret 1859, 

 pag. 251. 



Phascolosoma pusillum, M. Sars. 

 Yidenskabsselskabets Forhandlinger, Aaret 1868, named but 

 not described. 



Sipunculus aus Kilmore? Claparéde. 

 Müllers Archiv f. Anatomie u, Physiologie, Jahrgang 1861, p. 540. 



The body 3 Mm. long, 2 Mm. thick, pear-shaped, 

 everywhere covered with small conical papillæ (Tab. 15, 

 fig. 30 p), terminates behind in a little point, and shews 

 under a strong magnifying glass a reticulated appearance. 

 The proboscis is extremely thin and long, and when 

 completely extended measures up to 34 Mm. ; it is covered 

 with very fine papillæ, which are situated in regular 

 transverse rows and cease entirely about 3 Mm. from 

 the oral aperture. The latter is round and furnished 

 with very small soft prominences (fig. 30' o), formed by 

 the cylindrical epithelium which covers the interior sur- 

 face of the oesophagus; there are otherwise no tentacles. 

 The skin is rather firm and, when the proboscis is ex- 

 tended, so far transparent that the interior organs may 

 be seen, but still very indistinctly; its interior surface 

 is covered with the usual layer of connected annular and 

 longitudinal muscles, which are very thin. The layer of 

 epithelium is formed of very large cells, containing, be- 

 sides nuclei, a quantity of greenish pigment (fig. 33), 

 which gives to the skin its peculiar fine greenish color. 

 Only one retractor, which takes its issue from the hin- 

 dermost end of the perivisceral cavity with a broad base, 

 and then goes in the middle of the body and of the pro- 

 boscis, like a round column, right on to the oral aper- 

 ture, round which it is inserted (fig. 30 r, r, r, r). The 

 oesophagus, which is very long and narrow, accompanies 

 the retractor some way down into the perivisceral cavity 

 (fig. 30 sp, sp, sp), where it goes over into the intestine 

 (fig, 30 t, t), which forms a number of loose circumvolu- 

 tions on the left side of the retractor, extending nearly 

 to the posterior end; hence the intestine goes again for- 

 ward to a considerable distance, then bends backward, 

 and again goes forward over the retractor coming now 

 on the right side (fig. 30 t 1 ), where it forms sometimes 

 a few bends, which are attached by fine filaments to the 

 perivisceral cavity; sometimes spiral circumvolutions (fig. 

 30 1 2 ) which finally go over into a long nearly straight 

 rectum, which has its aperture on the proboscis a little 

 above its base (fig. 30 re, re). The segmental organ 

 forms an elongated clear bladder, the freely pendant ex- 

 tremity of which is conically tapered (fig. 30 s). In the 

 perivisceral cavity there are frequently a number of loose 

 ova. The nervous cord takes its beginning at the basal 

 part of the retractor, and runs along the interior surface 

 of the body and proboscis towards the anterior extremity 

 of the oesophagus, where, as in the Sipunculides, it usu- 

 ally forms a ring (fig. 30 n, n, n). The perivisceral cavity 

 and all the organs contained therein covered with the 

 peritoneum. 



