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13
Under Beskrivelsen af Slægterne Trochostoma og Irpa
gjorde vi opmærksom paa, at Stenkanaleii var fastvoxet til
Huden, uden at gjennembore den, og at der havde dannet
sig en Madreporplade paa selve Stenkanalen, indenfor
Til-hæftningspunktet, og vi antydede, at denne Ordning
mindede om en embryonal Tilstand. Hos Elpidia er
Stenkanalen ligeledes fastvoxen til den ydre Hud; men hos den
har ingen Madreporplade dannet sig, hvorved den end mere
end de to nævnte Slægter nærmer sig Larvestadiet, som
først hos Kolga er fuldkommen vedligeholdt.
Ihvorvel den paa Ryggen beskrevne Krave med de 6
Papiller ikke staar i nogen direkte Forbindelse med
Vand-karsystemet, saa maa de dog nærmest henføres dertil, da
de ’svare til Holothuridernes Rygfødder.
Paa den indre Flade af Kropshuden, paa det Sted,
der svarer til Kraven» findes et Hulrum, der er dækket af
et Diaphragma, hvori sees 4 aflange Aabninger, to til hver’
Side, Fig. 8, l, 12, h. Diaphragmaet er dannet af et
temmelig fast, hyalint Bindevævslag, samt Muskelfibre, og
har et Overtræk af det flimrende Peritoneum. Aabningerne
ere forsynede med cirkulære Muskelfibre, der danne en
Slags Sphincter, som bidrager til, at de kunne
sammentrækkes og udvides efter Omstændighederne. Borttager man
Diaphragmaet. iagttages en aflang Hulhed, der svarer til
Kravens Form, og i hvis Bund sees 6 runde Aabninger for
de hule Papiller. Saavel Hulrummet, som Hulheden i
Pa-pillerne ere beklædte med et flimrende Epithel. der er
Fortsættelse af Peritoneums. Kravens Hulhed, ligesom
Pa-pillernes, staa saaledes i umiddelbar Forbindelse med
Kropshulheden, og dennes Vædske cirkulerer derfor ind og ud
af dem og bidrager til. at de udspændes og. sammenfalder.
Selve Papillernes Struktur er den samme som Føddernes,
kun ligge Spiklerne noget mere adskilte fra hverandre,
naar undtages de øverste Spidser, hvor de ligge mere
compakte.
Blodkarsystemet.
De Blodkar, som strax springe i Øinene, naar Dyret
aabnes, er Tarmens Ryg- og Bugkar, eftersom Sectionen
sker fra Ryg- eller Bugsiden. Disse Kar udspringe jo hos
Holothuriderne i Almindelighed paa Grændsen imellem Mave
og Tarm; men saa er ikke Tilfældet hos Kolga. Her tage
de sit Udspring fra et ringformigt Kar, der omgiver
Svælget, Fig. 8, m, strax bagenfor Vandkarringen og tildels
dækket af denne.
Blodkarringen, der er tin som en Traad, afgiver fra
dens forreste Rand Grene til Svælget og et Par Grene til
Vandkarringen; fra dens bagerste Rand udgaar en Gren,
der bugter sig langs Spiserøret og Maven til Kjønsorga-
When describing the genera Trochostoma and Irpa,
we called attention to the fact that the sand-canal was
connate with the integument, which, however, it does not
perforate, and that a madreporic plate had developed on
the canal itself, within the point of attachment,
intimating that such organic arrangement was suggestive of an
embryonic state. In Elpidia, too, the sand-canal is
connate with the outer skin; but there is no madreporic
plate, and hence it approximates more closely than do
either of those genera to the larval stage, which in Kolga
is perfectly maintained.
The dorsal protuberance, or collar, with its (5
papillary warts, has, indeed, no direct connexion with the
aquiferous system, but must nevertheless be referred to that
part of the organism, being the analogue of the dorsal
suckers in other Holothurians.
On the inner surface of the integument, in
juxtaposition to the base of the collar, occurs a hollow space, covered
by a diaphragm, in which are seen 4 oblong openings, two
on either side. fig. 8, I; 12, h. The diaphragm consists of
a layer of rather firm, hyaline connective tissue, and of
muscular fibres, over which extends the ciliated peritoneum.
The openings are furnished with circular muscular fibres,
constituting, as it were, sphincters, that assist, when
needful, in their contraction and expansion. On removing the
diaphragm, an oblong excavation is observed, similar in
form to the collar, and in the bottom of which are seen 6
round apertures, for the reception of the hollow papillæ.
This hollow space, and the cavities of the papillæ, are
both covered with a ciliated epithelial membrane, a
continuation of that on the peritoneum. Hence, the hollow
interior alike of the collar and of the papillæ is in
direct communication with the perivisceral cavity,
affording ingress and egress to its fluid, which, circulating
freely through them, is partly the cause of their expansion
and collapse. The papillæ have the same structure as
the suckers; their spiculæ, however, are less closely set,
saving those on the extreme points, where a denser
arrangement is observed.
Circulatory System.
On opening tlie animal, the blood-vessels first
discerned are the dorsal and ventral vessels of the intestine,
according as the section be made on the dorsal or ventral
side. Now, these vessels originate in most Holothurians
between the stomach and the intestine; but Kolga forms
an exception to the general rule. In this genus, they. issue
from an annular vessel encircling the gullet, fig. 8, m,
immediately posterior to the water-vascular ring of the
ambulacral system, by which they are partly covered.
The circlet of blood-vessels, which is slender as a
fine-drawn wire, ramifies on the anterior margin, divers
branches protending to the gullet, and one or two to the
water-vascular ring: from the posterior margin a flexuous
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