Fordøielsesorganerne. 
Indgangen til Svelget, det saakaldte Atrium, har en 
stærk Sphincter, der dannes af Spisergrets Ringmuskler, 
idet disse forlænge sig op over den midterste Del af Mund- 
skiven, i hvis Centrum Atriet findes. Dette er forsynet 
med skarpt fremragende Længdefolder, der dog ganske ud- 
slettes, naar Mundaabningen er tilstreekkelig udvidet. Disse 
Folder blive ved Sphincters Sammentrekning saa skarpe, 
at enkelte Forfattere, f. Ex. Risso, har kaldt dem Tænder. 
Sveelget er cylindrisk, omtrent 10”” langt, strækker 
“sig mindst 5”” bagenfor Vandkarringen, er meget muskuløs, 
har en mere eller mindre intens brun. Farve, -og et smukt 
netformigt Udseende. Det er bundet til Kalkringen ved 5 
dobbelte Længderækker af Muskelbaand. Disse bestaa 
en eller flere Muskelbundter, som ere sammenbundne ved 
et stærkt fibrillært Bindevæv. Rækkerne synes at følge 
Kropsfelterne, saa at 3 falder paa Bugfladen og 2 paa Ryg- 
siden. I hver Række er der omtrent 10 Muskelbaand, der 
‘ere bredest udad mod Kalkringen, hvor de inserere sig paa 
Siden af Radialstykkerne. 
Svælget bestaar af de samme Hudlag, som hele den 
øvrige Tarmkanal, kun træde enkelte Lag i Svælget frem 
med større Styrke, end paa de øvrige Steder. Svælgets 
ydre Flade er beklædt med et flimrende Epithel, der egent- 
lig er Peritonealovertrækket; under dette findes et temme- 
lig tyndt, gjennemsigtigt Bindevæv, som er sparsomt paa 
Fibre, og hvori der ikke kunde iagttages Celler. Dette 
ydre Bindeveeyslag støder umiddelbart til Muskelhudens 
Ringmuskler, som her slutte sig tæt til hverandre, uden 
dog at være anderledes sammenhængende, end at der imel- 
lem hver Ringmuskel sees en fin Stribe af Bindevæv. 
Længdemusklerne staa noget længere fra hverandre, og idet 
de overskjære Ringmusklerne, faar Muskelhuden et gittret 
Udseende, ikke ulig Sipunkelhuden. Flere af Længdemusk- 
lernes Fibre anastomosere med hverandre. 
Indenfor Længdemusklerne findes atter en Bindevævs- 
hud, der bestaar af to Lag; det ydre Lag, der støder 
umiddelbart til Længdemusklerne, er stærkt fibrillært og 
optages næsten ganske af en rig, netformig Karudbredning; 
det indre Lag er meget tykkere, temmelig gjennemsigtigt, 
og i dette sees yderst fine Kalkkorn, hist og her enkelte 
Fibre, og endelig en Mængde spredte, aflange klare Celler, 
som indeslutte 8—12 gjennemsigtige Molekiiler, de samme, 
som tidligere ere omtalte i Hudens indre, hyaline Binde- 
vævslag. Paa dette indre Bindevævslag hviler EKpithelet, 
som er meget tykt, bestaar af flere Lag lange Celler (Oy- 
linderepithel), og udgjør den egentlige Slimhud, som her 
danner tætstaaende Længdefolder, der rage ind i Svælget. 
Hvor dette gaar over i Maven findes udvendig en Ind- 
snøring. 
ale 
47 
Digestive Organs, 
The entrance to the gullet, or atrium, as it is 
called, has a powerful sphincter. the annular muscles of 
the æsophagus being prolonged up over the medial portion of 
the oral disk, in the centre of which the atrium is located. 
The latter is furnished with acuminate projecting longitudi- 
nal folds, which, however, entirely disappear when the oral 
aperture is sufficiently distended. On ‘the contraction of 
the sphincter, these folds assume so acuminate an ap- 
pearance, that some authors, Risso for instance, have given 
them the name of teeth. 
The esophagus is cylindric in form, about 10”” Jong, 
extends 5”” atleast behind the water-vascular ring; is remar- 
kably muscular, of a more or less deep-brown colour, and 
It is webbed to the cal- 
careous ring by 5 double longitudinal series of muscular 
bands, which consist of one or more fascicles of ‘muscles, 
webbed together by a strong fibrillous layer of connective tis- 
has a fine reticulated appearance. 
sue. These series would seem to accompany the sections of the 
body, so that 3 belong to the ventral and 2 to the dorsal 
surface. Hach series is furnished with about 10 muscular 
bands, broadest externally towards the calcareous ring, 
where they issue from the sides of the radial segments. 
The æsophagus is composed of the same tegumentary 
layers as the intestinal canal; but several of the pharyn- 
geal layers exhibit greater density than do those of the 
latter organ. The outer surface of the esophagus is invested 
with a vibratile epithelium, in a strict sense the peritoneal 
tunic; beneath the latter extends a rather thin translucent 
layer of connective tissue, sparingly furnished with fibres, and 
in which no cells could be detected. This outer layer of con- 
nective tissue is connate with the annular muscles of the 
muscular tunic, between each pair of which, though their 
arrangement here is compatatively close, may be discerned 
a slender filament of connective tissue. A somewhat wider 
space intervenes between the longitudinal muscles, which, on 
« their intersecting the annular muscles, give to the skin a shiny, 
glittering appearance, not unlike that characterising the mus- 
cular tunic in Syunculus. Several of the fibres in the 
longitudinal muscles anastomose one with the other, 
Underneath the longitudinal muscles extends another 
stratum of connective tissue, composed of two layers; the outer 
layer, contiguous to the longitudinal muscles, is exceedingly 
fibrillous, and almost entirely composed of a reticulate vas- 
cular assemblage; in the inner layer, which is much thicker, 
are seen exceedingly minute calcareous granules, here and 
there, too, a few fibres, and, widely dispersed, numbers of 
bright elliptic-shaped cells, containing from 8 to 12 trans- 
lucent molecules, similar to. those, already described, in the 
inner hyaline layer of connective tissue. Over this inner layer 
of connective tissue extends the epithelium, which is very 
thick, consisting of several layers of elongate cells (the 
cylindric epithelium), and constitutes the mucous integument, 
which here forms closely arranged longitudinal folds, pro- 
jecting into the esophagus. On the outer surface of the latter, 
where it opens into the stomach, is seen a constriction. 
