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12
Bindevævet er dog overalt hyalint og rigt paa Kjærner.
Fødderne have den samme anatomiske Bygning, som
Huden, kun med den Forskjel, at i deres Hulhed ender en
Gren af Radialkarret blindt. Kalkspiklerne i Fødderne
ere to Slags, de smaa og de store, hvilke tidligere ere
beskrevne; de store ere dog tilstede i størst Mængde, ligge
baade paatvers og paaskraa, dog saaledes, at de paatvers
liggende ligesom omgive Foden og ere mere sammenpakkede
end de skraa, der ligge mere isolerede. Imod Fodspidsen
blive Kalkspiklerne mindre og spinklere, og ere her tildels
sammenflettede, uden dog at danne noget Net, Fig. 14.
Tentaklerne ere i det væsentlige bygget som Fødderne,
kun er deres Form meget forskjellig. Skaftet er cylindrisk,
glat og sparsomt forsynet med Kalk, og kun hist og her
sees en Spikel; paa Bladet, der er meget tykt, er det
Fligene og fornemmelig deres Rande, som have en bred Bræm
af tætbesatte Spikler. Paa dé tre store Lapper er den
midterste Flig næsten ganske indtaget af Spikler. Overalt
i Tentakelfligene findes afsat i Bindevævet dels under, dels
imellem Spikellaget en stor Mængde orangefarvet Pigment,
der ligesom i Mundskivehs Hud er snart samlet i Hobe,
snart indesluttet i spredte Celler.
Vandkarringen har som sædvanligt sine to Tilhæng,
nemlig den Poliske Blære og Stenkanalen. Den Poliske
Blære er meget stor, har en kort, men bred Hals, hvormed
den munder ud noget til Siden paa Ringkanalens Bugflade,
Fig. 8, e, 9, f. Dens Vægge ere temmelig tykke og have
samme anatomisk-histologiske Bygning, som Ringkanalen;
dog synes dens Muskulatur at være stærkere.
Stenkanalen, der er temmelig lang, næsten melkehvid,
ikke meget tyk, men fast, snor sig korketrækkerformigt
langs Udførselsgangen for Kjønsorganet, hvortil den er
bunden vecf et løst Bindevæv, Fig. 8, i, 29. a. Dens ydre
Ende, Fig. 8, k, 29, b, perforerer Huden omtrent paa
Midten af Halsen strax foran Kraven, hvor den udmunder paa
Hudens Overflade med en fin, rund Aabning, der er tæt
omgivet af større og mindre Spikler, Fig. 29, c. Dens
indre Ende munder ud som sædvanligt i Ringkanalen paa
Rygsiden, dog henimod dennes Sidedel. Stenkanalen dannes
af et tykt, hyalint Bindevævslag, og dens Lumen er beklædt
med flere Cellelag, hvoraf det inderste bestaar af lange,
flimrende Cylinderceller. Dette indre Epithel synes næsten
ganske at udfylde Hulheden. Kalk findes ikke i
Stenkanalen.
Her har man da en fuldstændig embryonal Tilstand,
forsaavidt Stenkanalen er forbleven aaben, hvorved
Vand-karringens Indhold umiddelbart korresponderer med
Søvandet. ,
organs in the Holothuriidæ; but the connective tissue is
everywhere hyaline, and highly nuclean.
The suckers are distinguished by the same anatomical
structure as the skin, saving that a branch of the radial
vessel terminates cæcally in their cavities. As already
described, the calcareous spiculæ in the suckers are of
two kinds — small and large; the large spiculæ, which
occur in the greatest numbers, exhibit some a transverse
and some an oblique arrangement, those transversely
disposed apparently circumscribing the sucker; moreover, they
are closer set than the oblique spiculæ, the latter being
comparatively isolated. Near the extremity of the sucker,
the calcareous spiculæ are smaller and more slender; here,
too, they are partly interlaced, without however being strictly
reticular, fig. 14.
The structure of the tentacles is essentially similar
to that of the suckers, their form, however, widely different.
The tentacular shaft is cylindric, smooth, and sparingly
furnished with calcareous deposit; and here and there only
does an isolated spicule occur; the lobes of the pinnæ, and
more especially their margins, are densely covered with
spiculæ. On the three large lobes, the medial lobule is
almost wholly occupied by spiculæ. Throughout the
connective tissue of the tentacular lobules, partly beneath, partly
between the spicular layer, is seen a mass of
orange-coloured pigment, occurring, as in the membrane of the oral
disk, either agglomerated in patches or deposited in cells.
The water-vascular ring has the two normal
appendages, viz. thePolian vesicle and the sand-canal. ThePolian
vesicle is very large, and furnished with a short, but broad
neck, through which, slightly deflected, it disembogues on
the ventral surface of the annular canal, fig. 8. e; 9, /.
The walls of the vesicle are rather thick, their
anatomic-histological structure being that of the annular canal; its
muscular development is however apparently greater.
The sand-canal, which is rather long, in colour
approaching to milky-white, not particularly thick, but firm
in texture, winds in a spiral coil along the eferent duct
of the generative organ, to which it is webbed by lax
connective tissue, fig. 8, i ; 29, a. Its outer extremity, fig. 8, k;
29, b, perforates the skin nearly in the middle of the
neck, immediately in front of the ucollar," at which
point it disembogues on the surface of the integument,
through a narrow, circular opening, densely bordered with
larger and smaller spiculæ, fig. 29, c. Its inner extremity,
as is commonly the case, opens into the vascular ring on
the dorsal side, but somewhat laterally. The sand-canal
is composed of diaphanous connective tissue, and has its
lumen covered with cellular layers, the innermost layer
consisting of long cylindric, cells, furnished with vibratile
cilia. The cavity would seem to be almost entirely filled
up by this inuer epithelium. No traces of calcareous
deposit in the sand-canal.
Here, accordingly, we have a true embryonic state,
inasmuch as the sand-canal still remains open, whereby
the water-vascular ring and its contents are kept in direct
communication with the sea-water.
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