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43
hvilken den smelter sammen og danner et bredt Belte,
Fig. 32. c, Fig. 34. a, der skjuler ganske et bagenfor
liggende, transverselt Septum, til hvis Midte det er
adhæ-reret, imedens der fra Beltets Siderande udgaa flere stærke
Bindevævstraade, som fæste sig til Coenenchymets indre
Væg, Fig. 32, d. Foruden at dette Belte er fæstet langs
Midten af det transverselle Septum, er det tillige
sammen-voxet til dettes nederste, fri Band, Fig. 34, b. Fjernes
dette Belte, saa .træder Septum transversale tydeligt frem,
Fig. 34. r; det er 2,5""" hoit, er fæstet paa begge Sider til
Coenenchymets indre Væg, Fig. 34, d, og deler det nederste
Hum i Stilken i to Dele, den ventrale og dorsale Kanal,
idet de laterale Kanaler egentlig ophorer der, hvor det
transverselle Septum optræder, Fig. 34, .e.
Septum transversale er dannet af en dobbelt
Binde-vævsmembran, der opad har en tyk Rand, Fig. 34,/,
hvortil det føromtalte Belte ogsaa er fæstet. Denne
Dobbel-membran folder sig saa, at en Del slaar sig bagover paa
Axeskeden, forlænger sig derefter nedover dennes forreste
Væg, omgiver Skedens nederste Ende og danner ligesom
en Sæk, hvori denne ligger; den forreste Del af Membranen
udgjør det egentlige transverselle Septum, hvis nederste,
fri Rand er nogle Millimeter fra Stilkens Bund. saa at
Enden af Axen «sees nedenfor den, Fig. 34, ff. Nedenfor
Septum transversale er der selvfølgeligt kun et eneste Rum,
hvori ikke alene den særdeles vide Dorsal- og Ventralkanal
aabner sig men ogsaa Sidekanalerne, idet Bunden af disse
sidste er gjennembrudt ved de mange Bindevævstraade,
hvorved Septa fæste sig til Coettenchymvæggen.
De dorsal-laterale Septa fæste sig indad paa
Axe-skedens Sidevæg, Fig. 35, a, lige ned til Axens Ende, Fig.
35, b[ men naar de komme i Niveau med det Steel, hvor
de ventral-laterale Septa, afgive den omtalte Fold, der
danner Beltet, sende de en meget stærk Fold fra sig. Fig. 35, c,
der bidrager væsentligt til Dannelsen af Septum transversale,
Fig. 35, d.
Unægteligt har det havt sine Vanskeligheder at
udrede disse temmelig indviklede Forholde i den bulbøse Del
af Stilken, og det lader sig derfor let forklare, at Dr.
Lindahl, der kun har havt et sparsomt Material, som han
ikke engang tilstrækkeligt har kunnet benytte, har
misforstaaet disse Forholde. Han har ganske overseet baade det
beskrevne Belte og Septuiu transversale; han udtaler sig
nemlig saaledes: " Umbellula’s skaft har i sin nedersta
del en helt egendonilig bygnad, idet att ändblasan utgöres
af den utvidgade nederste änden af ventralsidans
hufvud-kanal, hvars båda sidoväggar, de ventrala-laterala septa, böja
sig in under de ("tfrige tre hufvudkanalerna, så att de bilda
deras botten. Nämnda septa göra dervid et starkt veck
inwards, in front of the sheath of the axis, and meets
at the middle of the ventral surface, a corresponding fold
from the other side, with which it becomes fused, forming
a broad band (fig. 32, c, Pl. IX, fig. 34, «) that
completely conceals a transversal septum which lies behind
it, and to whose middle it is adherent; whilst, from the
lateral margins of the band; several strong filaments of
connective-tissue proceed, which are secured to the inner
wall of the sarcosoma (fig. 32, d). Besides this band being
adherent along the middle of the transverse septum, it is,
also, concreted with the inferior free margin (fig. 34. b).
If this band is removed, the septum-transversale becomes
distinctly prominent (fig. 34, c); it is 2.5""" high, and is
attached on both sides to the inner wall of the sarcosoma
(fig. 34, d) dividing the inferior space in the stem, into
two parts, viz. the ventral and the dorsal canals; because,
the lateral canals really cease at the point where the
transversal septum appears (fig. 34, e).
The septume-transversale is formed, of a double
membrane of connective-tissue, with a thick superior
margin (fig. 34, f) to which the band previously spoken of, is
also attached. This double membrane folds itself, in such
manner, that a portion folds backwards on the sheath of
the axis, then extends itself down along it’s anterior wall
and surrounds the inferior extremity of the sheath, forming,
as it were, a bag, in which it is enclosed. The anterior
part of the membrane forms the real transverse septum,
whose inferior free margin is distant, a few millimetres
from the base of the stem, so, that the extremity of the
axis is observable below it (fig. 34, ff). Below the septum
transversale, there is, consequently, only a single space, in
which, not only, the tolerably wide dorsal and ventral
canals open, but, also, the lateral canals; as the bottom
of these last, is perforated by the numerous
connective-tissue filaments by which the septa are .attached to the
wall of the sarcosoma.
The dorso-lateral septa are attached, inwards, to the
lateral wall of the sheath of the axis (fig. 35, a), right down
to the extremity of the axis (fig. 35, b); but, when they
come in line with the point where the ventro-lateral septa,
produce the fold spoken of as forming tbe band, they push
forward a very strong fold (fig. 35 c) which contributes,
principally, in the formation of the septum-transversale
(fig. 35, d).
The clearing up of these rather complex relations in
the bulbous part of the stem, has, undeniably, had it’s
difficulties; and, it is, therefore, easy to understand, how Dr.
Lindahl, who had only slight material to work with, and
which, he was not, even, in a position to sufficiently utilise,
has misunderstood these relations. He has quite overlooked
both, the band and the septum-transversale, which we have
described. He states the following: " Umbellula’s shaft
has, in it’s lower part, a quite peculiar structure,
inasmuch,that the terminal vesicle is formed by the dilated
lower extremity of the main canal of the ventral side,
through both of whose lateral walls, the ventro-lateral septa
curve in, under the other three main canals, so, that they
f>*
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