38 



ligesom ind i samme, saa det ser ud, som de her ere ud- 

 gaaede fra Ectoderraet. 



Der er 6 Par principale. fuldstændige Septa. som ere 

 tykkere og fastere end alle de øvrige; de fæste sig meget 

 stærkt paa Svælgrøret (Øsophagus) og ere golde. Af disse 

 principale Septapar er der 2 Par Retningssepta, hvoraf 

 det ene Par er noget bredere end det andet, det vil sige, 

 Septa staa længere fra hinanden, hvorved det intraseptale 

 Rum bliver bredere. De indre Flader af Retningssepta 

 ere beklædte med transverselle Muskler, der altsaa vende 

 mod hverandre, medens de ydre Flader have longitudinelle 

 Muskler, som vende fra hverandre. De øvrige 4 Par Septa 

 adskille sig fra Retningssepta ved en forskjellig Anordning 

 af Musklerne, idet de longitudinelle Muskler hekkede de 

 indre Flader. vende mod hverandre og vise sit; som foldede 

 Blade, der ganske udfylde de intraseptale Rum ; de trans- 

 verselle Muskler sidde paa den ydre Flade. ere ikke saa 

 stærkt udviklede og vende mod det interseptale Rum. 



De sekundære Septapar ere 18. fæste sig ikke paa 

 Svælgrøret, men naa næsten hen til samme. De ere paa 

 deres indre Flader beklædte med stærke, longitudinelle 

 Muskler, som vende mod hverandre, imedens de ydre Flader 

 ere forsynede med transverselle Muskler. Disse have Ud- 

 seende af en foldet Lamel, som er temmelig tyk, imedens 

 de longitudinelle Muskler danne Buske, der for en Del 

 udfylde det intraseptale Rum af de sekundære Septa. Disse 

 bære Mesenterialfilamenter og muligens Acontier, men ere 

 forresten golde. De fleste Acontier fandtes paa de Exem- 

 plarer, hvor Svælgrøret var noget udkrænget, og udfyldte 

 Mundaabningen ; i Kamrene saaes kun enkelte. 



r 



De tertiære Septa udgjøre 24 Par; de ere korte, 

 neppe halvt saa lange som de sekundære og bære Genera- 

 tionsorganerne, hvori sees en Mængde forskjelligt udviklede 

 Æg. Paa deres indre Flade sees de transverselle Muskler, 

 som en fynd, foldet Lamel, hvorfor de intraseptale Rum 

 her ere temmelig vide. Tab. VIII, Fig. li d; den ydre 

 Flade er beklædt med de longitudinelle Muskler, som ere 

 vel udviklede. Tab. VIII, Fig. 6 e. Kjønnene synes at 

 være adskilte; idetmindste har jeg ikke fundet Testikler 

 der. hvor jeg har fundet Ovarier. 



Findested. 



Station 370. 3 Exemplarer, der alle sad paa Fusus 

 Kroyeri. og hvoraf 1 var særdeles stort. 



Station 374 ligeledes 3 Exemplarer. som ogsaa 

 sad paa samme Mollusk's Oonchylie, og hvoraf 1 havde 

 samme Størrelse som det største paa Stationen 370. 

 Samtlige Mollusker vare levende og spadserede noksaa hur- 

 tigt omkring i Observationskarret, dragende paa Actinien, 



lie rather elose to the ectoderm. and some even. extend 

 themselves as it' into it. so that it almost appears here 

 as if they issued from the ectoderm. 



There are 6 pairs of prineipal. perfect septa. which 

 are thicker and finner than all the rest ; they attaeh 

 themselves very firmly to the cesophagus aud are sterile. 

 Of these pairs of prineipal septa, 2 pairs are directive 

 septa. of which the one pair is somewhat broader than 

 the other; that is to say, each septum stands farther apart 

 from the other. so that the intraseptal space is broader. 

 The inner surfaces of the directive-septa are clad with 

 transversal muscles, which consequently face towards each 

 other. whilst the outer surfaces have longitudinal muscles 

 and face from each other. The remaining 4 pairs of septa 

 are distinguished from the directive septa by a different 

 arrangement of the muscles; thus the longitudinal muscles 

 clothe the inner surfaces. face towards each other. and 

 appear as folded laminæ which quite flll the intraseptal 

 spaces; the transversal muscles are placed on the exterior 

 surface, are not so strongly developed, and face towards 

 the interseptal space. 



The secondary pairs of septa are is j n aumber, and 

 do not secure themselves to the oesophagus hut reach 

 almost to it. On their inner surfaces. they are clad with 

 strong longitudinal muscles which face towards each other. 

 while the outer surfaces are furnished with transversal 

 muscles. These have the appearance of a folded lamell. i 

 which is rather tbick, while the longitudinal muscles tonn 

 frutici that to a certain extent fill the intraseptal spaces 

 of the secondarj septa. These carry mesenterial filaments, 

 and possibly also acontia, hut are sterile. Most of the 

 acontia were found on those specimens where the oesoph- 

 agus was somewhat everted and filled the oral aperture; 

 in the chambers only few were seen. 



The tertiary septa. consist of 24 pairs; they are 

 short. scarcelj half the length of the secondary septa, aud 

 carry the reproductiv-e organs, in which a multitude of 

 varioush developed ova were observed. On their inner 

 surfaces. the transversal muscles are seen like a thin folded 

 lamella, for which reason the intraseptal spaces are. here, 

 rather wide (Pl. VIII. fig. 6 d). The exterior surface 

 is clad with the longitudinal muscles. which are well 

 developed (Pl. VIII. fig. 6 e). The sexes seem to be 

 separated; at all events. I have not observed testicles 

 where I found ovaries. 



Habitat. 



Station No. 370. Three specimens; all of which were 

 seated upon Fusus Kroyeri. and one of which was par- 

 ticularly large. 



Station No. 374. Also three specimens here; seated 

 on the same mollusc's shell, and one of them was of the 

 same size as the largest one from station No. 370; all 

 the molluscs were alive. and perambulated quite activeiy 

 about the glass vessel, bauling the aetinia along with them; 



