93 



har en lateral Zooidstribe, der er temmelig lang og fort- 

 sætter sig opad i de rudimentære Finner, som i Begyn- 

 delsen fremtræde som svage Tverlinier paa hver Side af 

 Stokken, men blive alt høiere og høiere jo længere de 

 komme op paa Rachis, indtil den rudimentære Finne er 

 dannet. De rudimentære Finner dannes derved, at Poly- 

 pernes Grunddel er paa Siderne sammenvoxet, saaledes 

 at begge de ydre Polypers udvendige Vægge ere frie og 

 gaa umiddelbart over i Sarcosomaet. Naar derfor kun 2 Po- 

 lyper staa sammen, existerer aldeles ingen Finne; thi da ere 

 disse Polyper sammenloddede ved deres indvendige Flader 

 lige nede ved Basaldelen, strax efter at de træde ud af 

 Sarcosomaet. De have Udseende som om de sidde umid- 

 delbart paaRachis. Ere 3 Polyper grupperede sammen, bliver 

 ved den omtalte S ammenvoxning en SlagsFinne dannet; men 

 dog væsentlig forskj eilig fra den, som findes hos Slægterne 

 Virgularia og Stylatula. Denne rudimentære Finne, lige- 

 som Polypgrupperne, støttes af en Kalkplade, der kun 

 lidet afviger fra den, der findes hos Stylatula. 



Saavel paa Ventral- som Dorsalfladen findes temme- 

 lig tydelige Vulster, som især ere iøinefaldende i Nær- 

 heden af Polyperne og fremkomme ved de radiære 

 Kanaler. 



Zooiderne ere altid laterale, men strække sig mere 

 over paa Dorsalfladen, hvor de som oftest danne flere 

 Rækker (Tab. 3, Fig. 3 b, 5 b). 



Den indre Bygning er o'gsaa noget afvigende fra de 

 nærstaaende Slægter. 



Stilkens Endeblære, ligesom hele den pulpøse Del 

 er forsynet med Længdemuskler, der baade ere i rigelig 

 Mængde tilstede og stærkt udviklede. Circulære eller 

 Tvermuskler findes ikke. Septum transversale har vel et 

 Centrum, der er optaget af Saftkanaler (Tab. 12, Fig. 2 1"); 

 men ingen Stræng, som Kölliker anfører hos Virgularierne. 

 Saavel i Huden, som i Sarcosomaet ere Kalkkorn ind- 

 sprængte, og i den øverste Del af Stilken findes hist og 

 her Kalknaale. 



Slægten Diibenia har ligesom de øvrige Virgulariner 

 4 Længdekanaler (Tab. 10, Fig. 9 d, v, S, S), som dog i 

 StilkeDs nederste Del smelte sammen til 2, en Ventral- 

 og en Dorsalkanal (Tab, 12, Fig. 2 v, d), i denne sidste 

 ender Axen. Foruden disse 2 Kanaler findes i den øver- 

 ste Del af Stilken og i hele Stokken 2 Sidekanaler (Tab 10, 

 Fig. 9 s, s), der ere smalere end de to foregaaende. 

 Disse 4 Kanaler omgive Axen. Fra Dorsal- og Ventral- 

 kanalen udgaa mange radiære Kanaler (Tab. 10, Fig. 11 rd, 

 rd, rv, rv), der ikke alene correspondere med Polyperne 

 (Tab. 12, Fig. 1 rv, rv, rv), men ogsaa danne ved Boden 

 af hver Polypgruppe (den rudimentære Finne) en Vulst 

 saavel mod Ventral- som Dorsalfladen (Tab. 10, Fig. 10 

 rv, rd). Foruden disse Kanaler findes et tæt longitudinelt 

 Kanalsystem (Tab. 12, Fig. 1 1), der med Tvergrene ana- 

 stomosere med hinanden indbyrdes og har Forbindelses- 

 grene med Ventral- og Dorsalkanalen (Tab. 12, Fig. 2 1; 



band of zooids which is rather long and is continued 

 upwards in the rudimentary fins, which latter appear at 

 first as faint transverse lines on each side of the polypary, 

 but become higher and higher the further they advance 

 on to the rachis until the rudimentary fin is formed. 

 The rudimentary fins are formed by the basal part 

 of the polyp being connate on the sides; so that 

 both the outward walls of the exterior polyps are free, 

 and go immediately over into the sarcosoma. When 

 therefore only 2 polyps stand together, no fin at all 

 exists; for then these polyps are soldered together 

 by their interior surfaces right down to the basal 

 part, just as they issue from the sarcosoma. They 

 have the appearance of being situated immediately on 

 the rachis. When 3 polyps are grouped together, a sort 

 of a fin is formed by the attachment described, but yet 

 essentially different from that which exists in the genera 

 Virgularia and Stylatula. This rudimentary fin, as also 

 the groups of polyps, is supported by a calcareous plate 

 which only in a slight degree differs from that found in 

 the Stylatula. 



As well on the ventral as on the dorsal surface there 

 are distinct swellings, which are especially remarkable in 

 the vicinity of the polyps, and produced by the radial 

 canals. 



The zooids are always lateral, but extend more over 

 on the dorsal surface, where they most frequently form 

 several rows (Tab. 3, fig. 3 b, 5 b). 



The interior structure is also somewhat different 

 from that of allied genera. 



The terminal bladder of the stalk, like all the pulpous 

 part, has longitudinal muscles, which both exist in abun- 

 dant number and are strongly developed; circular or 

 transverse muscles are not found. The septum trans- 

 versale has indeed a centre which is occupied with sap- 

 canals (Tab. 12, fig. 2 1"), but no chord, as (noticed by 

 Kölliker) in the Virgularia. As well in the skin as in the 

 sarcosoma, there are calcareous granules scattered; and 

 in the upper part of the stalk, there are here and there 

 calcareous needles. 



The genus Diibenia has, like the other Virgularieæ, 4 

 longitudinal canals,^ (Tab. 10, fig. 9 d, v, S, S) which 

 however in the lower part of the stalk are united in 2, 

 a ventral and a dorsal canal (Tab. 12, fig. 2 v, d) and 

 in the latter the axis ends. Besides these 2 canals, there 

 are in the upper part of the stalk and in the whole 

 polypary, 2 lateral canals (Tab. 10, üg. 9 s, s) which are 

 narrower than the 2 previous. These 4 canals surround 

 the axis. From the dorsal and ventral canals there pro- 

 ceed many radial canals (Tab. 10, fig. 11 rd, rd, rv, rv) 

 which not only correspond with the polyps (Tab. 12, fig. 1 

 rv, rv, rv) but also form at the root of each group of 

 polyps (the rudimentary fin) a swelling as well towards 

 the ventral as towards the dorsal surface (Tab. 10, fig. 10 

 rv, rd). Besides these canals, there is a compact longi- 

 tudinal system of canals (Tab. 12, fig. 1 1) anastomosing 

 by transverse ramifications with each other and commu- 



13 



