89 



semi danner lange Cylinderceller. der paa deres fri Ende 

 har en temmelig lang Pidsk (Geissei). Ved Længdesnit, 

 Tah. XI. Fig. 5 d, vise de endodermale Cirkulærmuskler sig 

 at ligge i tykke Bundter. 



Paa Tentaklerne er det egentlige Ectoderm noget 

 bredere end paa Kroppen. Foruden de alnrindelige, lange. 

 cylinderformede Epithelceller lindes der imellem disse 

 mange encellede, kolbeformede Slimkjertler, Tab. XL Fig. 

 4 a. samt en Mængde Nematocyster, Tab. XI. Fig. 4 b. 

 Indenfor Ectodermet, lige i Randen af det fibrillære Binde- 

 vævslag, er der et Lag stærke. longitudinelle Muskler, som 

 bundtevis ligge ligesom indkapslede i Bindevævet, Tab. XI. 

 Fig. 4 r. Fra dettes indre Flade udgaa Forlængelser i 

 næsten alle Retninger, hvilke anastomosere med hverandre 

 og danne derved et tæt Kanalsystem, hvis Vægge ere be- 

 klædte med Epithel, Tah. XI. Fig. 4 il. Paa et Tversnit 

 faar denne Mængde Kanaler Udseende af et Netværk 

 med store Masker, Tab. XI. Fig. 4 d. Det forekom mig. 

 at der paa Bindevævslagets indre Flade. hvorfra de be- 

 skrevne Forlængelser udgaa. laa et yderst smalt Lag at' 

 trausverselle Muskler. Tab. XI. Fig. 4 e; men det tør 

 hænde, at det var Bindevævsfibriller, som let kan foryéxles 

 med Muskelfibriller. 



Paa Kroppens nederste, inkrusterede og udvidede Ende 

 (Physa) viser et Tversnit. at indenfor Ectodermet. Tab. XI. 

 Fig. 9 fl, eller rettere, just der. hvor dette støder til Binde- 

 vævet, Tah. XI. Fig. 9 b. ligger et ganske særegent Lag, 

 bestaaende af Grupper af store Celler med en meget stor 

 Kjerne, omgivet at et rigl Protoplasma. Tab. XI. Fig. 9 c. 

 Disse Celler ere lidt atiange og fra den Ende. der vender 

 mod Ectodermet. udgaar jævnlig 1. sjelden 2 Udløbere, som 

 tabe sig i eller imellem Ectodermcellerné. Formlen disse 

 ('eller, som antagelig ere GanglieceBer, tindes der under 

 eller bag dem et Belte af meget mindre, runde, temmelig 

 klare Celler med deres Kjerne, hvilke ligesom hvile paa 

 et smalt Stratum af yderst fine Fibriller, Tab. XL Fig. 9 il 

 Jeg kan ikke henføre de her beskrevne Elementer til noget 

 andet histologisk Væv end et Nervéappara.ts. Det rykke- 

 des mig ikke at tinde noget lignende paa Mundskiven eller 

 omkring den øverste Svælgrørsaabning, ihvorvel det er sand- 

 synligt, at noget saadant tindes der: imidlertid er det at 

 lægge Mærke til. at denne nederste Del af Dyret er i 

 høieste Grad ømfindtlig, saa at den letteste Berørelse her 

 fremkalder stærke Kontraktioner og ormformige Bevægelser. 



Der er i; Par fuldstændige Septa, Tah. XI, Fig. 3, 

 8, 11, som tåge sin Begyndelse i Bundens Centrum af 

 Physa; hvert Pars Skillevægge ligge her saagodtsom i 

 Berorelse med hinanden; etterhvert som de straalefor-migt 

 forlænge sig opover Scapus. vige de mere fra hinanden Tab. 

 XI. Fig. 8, og blive bredere, saa at de. naar de have 

 naaet op til Svælgrøret, hvorpaa de fæste sig. danne 2 lige 

 brede Blade, der staa uogle Millimeter fra hinanden. Tah. 

 XI. Fig. 3, lirt. Af de 6 Par fuldstændige Septa er der 



Den norske Nordhavsexpedition. D. C. Danielssen: Actinida. 



some extent, by the endothelium, which forms long cylinder- 

 cells, which upon their free extremity have a rather long 

 flagellum (Geissel). In longitudinal sections (Pl. XI. fig. 5 <1). 

 the endodermal circular muscles slu, w themselves lying in 

 thick taseiculi. 



Upon the tentacles the real ectoderm is somewhat 

 broader than on the body. Besides the usual, long cylindrie- 

 cells, there are fouiul. amongst them, nunierous unicellular. 

 claviform mucous glands (Pl. XI, fig. 4 a), also a mul- 

 titude of nematocysts (Pl. XI. fig. 4 b). Inside of the 

 ectoderm, quite in the margin of the fihrillar layer ol' 

 connective-tissue there is a layer of strong longitudinal 

 muscles. which be in fasciculi. encapsuled, as it were, in 

 the connective-tissue (Pl. XI, fig. 4 c). From the inner 

 surface of the connective-tissue, prolongations issne in almosi 

 all directions; these anastomoze with each other, and thus 

 form a compact ductiferous system whose walls are clad 

 with epithelium (Pl. XI, fig. 4 d). In a transversal sec- 

 tion this mass of ducts acquires the appearance of a retic- 

 ulation with large meshes (Pl. XI. fig. 4 d\. It appeared 

 to me that. upon the inner surface of the laver of con- 

 nective-tissue from which the prolongations issne, there lav 

 an extremely narrow laver of transversal muscles (Pl. XI. 

 fii:. 1 e), hut it may he that these were connective-tissue 

 fibrils. which can easily be mistaken for muscle fibrils. 



In the lowest. encrusted and expanded extremity ut' 

 the body (physa) a transversal section shows, that inside 

 of the ectoderm (Pl. XI. fig. 9 a), or more correctly. just 

 at the point where it meets the connective-tissue (Pl. XI. 

 fig. 9 b) there lies a quite peculiar laver, consisting of 

 iiroups of large cells with a very large nucleus surrounded 

 by a rich protoplasm (Pl. XI. fig. 9 c). These cells are 

 slightly oblong, and from the extremity that faces the 

 ectoderm there issiies. generally 1. seldom 2 prolongations. 

 which loose themselves in. or between. the ectoderm cells. 

 Besides those cells. which are probably ganglial cells, there 

 is found below or behind them, a belt of much smaller. 

 round, rather pellucid cells with their nuclei. which. as it 

 were. rest upon a narrow stratum of extremely tine fibrils 

 (Pl. XI. fig. 9 il). I can not relegate the elements here 

 described to any other histological tissue than that of a 

 nérvous system. I did not succeed in tinding any thing 

 similar on the oral disc or round the uppermost cesophageal 

 orifice. although it is probable that something of the kind 

 is found there. It is. in the meantime. to be rémarked, 

 that this lowest part of the animal is sensitive in the 

 highest degree. so that the least touch produces, here, 

 strong contractions and vermicular movements. 



There are 6 pairs of perfect septa (Pl. XI. figs. 3. 

 8, 11) which originate in the centre of the base"of the 

 physa; the divisional walls of each pair of septa be 

 here almost in contact with each other; as they prolong 

 themselves gradually. radially, upwards over the scapus. they 

 open out more apart from each other (Pl. XI. fig. 8) and 

 become broader. so that when they have reached up to 

 the æsophagus, upon which they secure themselves, thej 

 form 2 equally broad laminæ, which stand a few milliinetres 



1-2 



