139 



Ved yderst tynde Tversnit viser sig Svælgrøret histo- 

 logisk at beståa af en Epithelbeklædning paa dets ydre 

 Flade (indre, Vogt), dannet af et cylindercellet Endothel, 

 lignende det, som beklæder hele Gastro vascularhulhedens 

 Vægge, Tab. XXV. Fig. 12 a; til dette Endothel støder 

 et Lag af Længdemnskler. Tab. XXV Fig. 12 b. der ere 

 festede til et hyalint Bindevævslag, Tab. XXV. Fig. 12 c. 

 paa li vis indre Flade lindes en Epithelialbeklædning, som 

 er forskjellig paa de forskjellige Steder; Bindevævet i den 

 store Svælggrube er lidt bredere end paa de øvrige Steder, 

 Tab. XXV, Fig. 12 d, og her sees Epithélet at beståa af 

 temmelig brede, ikke rnegej høie Cylinderceller, der ere 

 forsynede med Cilier og danne en jævn Flade mnd Svælg- 

 rørshulheden, Tab. XXV. Fig. 12 e; ogsaa i den lille 

 Svælggrube er et lignende Epithel, Tab XXV. Fig. 11 «; 

 men til Siderne af begge Svælggruber, hvor Væggen er 

 meget foldet og derfor ujævn, dannes disse Folder af 

 smale, listeformige Forlængelser lia Bindevævet, der rage 

 ind i Hullieden og eie beklædte med temmelig lange Cylin- 

 derceller. som vifteforniigt ere festede til Bindevævslisterne, 

 Tab. XXT'. Fig. 11 b. 12/. 



Der er 36 fuldstændige Septa, livoraf 4 kunne be- 

 tragtes som Retningssepta, eller et Par ventrale og et Par 

 dorsale, og ])aa hver Side af disse. S Par laterale Septa. 

 Alle disse Septa, der tåge deres Udspring fra Kropsvæg- 

 gens indre Flade og feste sig paa Onderfladen af Mund- 

 skiven og paa Svælgrørets ydre Væg, have en forskjellig 

 Længde. De ventrale Retningssepta, som feste sig paa 

 Svælgroret just paa det Sted. der indvendig svarer til den 

 ventrale Svælggrube. ere tykke. Tab. XXV. Fig. X d. 11 c. 

 1- g, og paa deres ydre Side, den der vender mod det 

 tilstødende, interseptale Kammer, forsynede med Længde- 

 muskler, Tab. XXV. Fig. 12 h, som henimod Svælgrørs- 

 inseitionen og ved Udspringet af Kropsvæggen ere tem- 

 melig tykke; paa deres indre Side, der vender mod det 

 intraseptale Kammer, ligge fine Tvermuskelfibre i Form 

 af en yderst tynd Membran. Tab. XXV, Fig. 12 i. Dette 

 intraseptale Kammer, Tab. XXV. Fig. 8 e; Tab. X XV. 

 Fig. 11 d. 12 k, som Professor C. Vogt med Rette kalder 

 ..la loge ventrale impaiiv. har en aflang, næsten triangulær 

 Form, og adskiller sig let fra de øvrige. De ventrale 

 Retningssepta strække sig et Stykke nedover (bagover) 

 Kroppens Bugflade, hvor de bidrage til at danne en indre 

 Bugfure. som senere skal omtales. 



De dorsale Retningssepta, Tab. XXV. Fig. S /'. 11 e, 

 ere temmelig tynde ; Længdemusklerne ligge ogsaa her paa 

 den ydre Side. imedens Tvernuisklerne beklede den indre, 

 som vender mod det intraseptale, dorsale Kammer, der er 

 aflangt, meget bredere end de nærmest tilstødende Kamre, 



contrasted with the lateral portions, which are strongly 

 folded (Pl. XXV. fig. 8 c). 



lu extreinely 1 1 liii transversal sections the 1 æsophagus 

 shows itself, histologically speaking, to consist of an epit- 

 helial covering on its outer surface (inner, Vogt.), formed 

 of an endothelium of cylinder-cells resembling tliat which 

 clothes the walls of the entire gastro-vascular cavity (Pl. 

 XXV. fiji. 12 a). To tliis endothelium a laver of longi- 

 tudinal muscles unites (Pl. XXV. fig 12 6); these are 

 adherent to a laver of hyaline connective-tissue (Pl. XXV. 

 fig. 12 c) upon whose inner surface an epitheliål covering 

 is found, which is. however, different in the different situa- 

 tions. The connective-tissue in the large gullet-groove is 

 a little broader than in the other situations (Pl. XXV. 

 fig. 12 (/). and heiv the epithelium is seen to consist of 

 pretty broad, not very high cylinder-cells. which are fur- 

 nished with eilire and form an even surface towards the 

 cavity of the gullet-tube (Pl. XXV. fig. 12 e); in the small 

 gullet-groove. also. there is a similar epithelium (Pl. XXV, 

 fiti. 11 «); but to the sides of botli the gullet-grooves, 

 where the wall is much folded and therefore uneven, these 

 folds are formed of narrow fillet-forined prolongations from 

 the connective-tissue, that project into the cavity and 

 are clad with rather long cylinder-cells. which, fan-like. are 

 secured to the connective-tissue fillets (Pl. XXV. fig. 11 b, 

 12/). 



There are 36 perfect septa. of which 4 may be 

 regarded as directive septa. or one pair ventral and one 

 pair dorsal; and upon each side of these again 8 pairs of 

 lateral septa. All those septa. which have their origin 

 in the inner surface of the wall of the body and secure 

 themselves to the under surface of the oral disc and the 

 outer wall of the æsophagus, have different lengths. The 

 ventral directive septa. which attach themselves to the 

 æsophagus just in the situation that corresponds, inter- 

 nally, to the ventral gullet-groove are thick (Pl. XXV. fig. 

 8 d, 11 c, 12 ff), and on their outer side, that which 

 faces towards the adjoining interseptal chamber, are fur- 

 nished with longitudinal muscles (Pl. XXV. fig. 12 //). 

 which. towards their insertion in the æsophagus aud at 

 the origin in the wall of the body, are pretty thick; upon 

 their inner side. which faces towards the intraseptal chamber. 

 there He delicate transversal muscle-fibres in the form of 

 an extremely thin membrane (Pl. XXV. fig. 12 i). This 

 intraseptal chamber (Pl. XXV. fig. 8 e, 11 </. 12 k) which 

 Prof. 0. Vogt rightly terms ,.la loge ventrale impaire" 

 has an oblong, alniost triangular form, and is easily dis- 

 tinguished from the others. The ventral directive septa 

 stretch themselves a little way downwards (backwards) 

 along the ventral surface of the body. where they con- 

 tribute to form au internal ventral furrow. which will sub- 

 sequently be spoken of. 



The dorsal directive septa (Pl. XXV, fig. 8/ 11 é) 

 are pretty thin ; also heiv the longitudinal muscles are 

 situated on the outer side. while the transversal muscles 

 clothe the inner one. which faces towards the intraseptal, 

 dorsal chamber; this is oblong. much broader than the 



is - 



