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40
den har temmelig tykke Læber.- som ligge næsten til
hinanden, uden ganske at slutte sig sammen.
I Bunden af denne Spalte syntes der at være flere
fine Aabninger, men som paa Grund af Dyrets Opbevaring
i Spiritus vare saa sammentrukne, at de ikke med
Bestemthed kunde sees, selv med stærk Loupe.
Bagenfor Tilhængets Grund paa Bugfladen iagttoges
den runde Mundaabning, Fig. 13, b, der er stærkt foldet,
og lidt til Siden af Mundaabningen. noget bagenfor denne,
sees en yderst lille, rund Aabning.
Huden er tyk, temmelig fast og ganske
uigennemsigtig paa Kroppen, imedens den paa Snabelen er noget
tyndere og gjennerasigtig. Den dannes af en Cuticula, Fig.
14, a, der er glasklar, uden Stribning og meget tynd paa
Kroppen, saa at den endog er vanskelig at iagttage uden
ved meget stærk Forstørrelse; paa Snabelen er den derimod
meget tykkere, Fig. 15, a.
Indenfor Cuticula er Epithelet, som dannes af et Lag
Cylinderceller, der have en bleg, gulgrøn Farve, ere 0.060mm
lange, 0.008mm brede ved deres Grunddel. De blive
smalere jo mere de nærme sig Overhuden og faa her Udseende
af en Række Orgelpiber, Fig. 14, b. 15, b.
Disse lange Cylinderceller have temmelig tykke Vægge.
..ere forsynede med en stor mørkere Kjerne og et noget
lysere Kjernelegeme, hvilke ere omgivne af et finkornet
Protoplasma.
Umiddelbart til dette Epithellag støder den egentlige
Cutis, der udgjør et tykt. hyalint Bindevævslag, hvori findes
en Mængde noget forskjelligt formede Bindevævslegemer.
Fig. 14, c; 15, c.
Indenfor Bindevævslaget er Muskelhuden, der dannes
af 3 Lag: det ydre; circulere Lag (Ringmusklerne), som
er temmelig bredt med stærke, tæt i hinanden liggende
Muskelfibre, som ere sammenbundne med Bindevæv, Fig.
14, d; det midterste Lag (Længdemusklerne), der ere
bredere end de ydre Ringmuskler, Fig. 14, e, og hvis Fibre
ere tykkere, og det indre Ringmuskellag, som er yderst
smalt, og hvis Fibre ere meget tyndere end de to
foregaaendes. Fig. 14, /. Det indre. Ringmuskellag er beklædt
af Peritoneum, der har et Epithelovertræk; om dette er
flimrende, hvilket er sandsynligt, kunne vi ikke afgjøre. .
Paa Snabelen ere Cylindercellerne noget kortere, og
her ligge Fibrene i Muskellagene saa langt fra hverandre,
at Muskelhuden er tydelig gittret.
Paa den indre Flade af Huden, just paa det Sted,
der svarer til den tidligere beskrevne Spalte paa liver Side
af den forreste Kropsende, sees en Række runde
Aabninger (vi talte 4 paa hver Side), hvilke vare omgivne af en
rund Vold. der dannede ligesom en Sphincter om
Aabnin-gen, som førte ind til Spaltens Bund, Fig. 11, a. 12, a.
Her er et Slags Respirationsapparat, hvorved Søvandet
posterior, slightly inclining towards the dorsal surface; it
has comparatively thick edges, near together, but not
contiguous.
The bottom of this fissured opening was apparently
pierced with divers minute apertures, which, however, had
become so shrunk and contracted (the specimen was
preserved in spirits) that even under a powerful lens they
could not be plainly distinguished.
Posterior to the base of the appendix, on the ventral
surface, is seen the round buccal aperture, fig. 13, b,
prominently folded; and a little aside of, and posterior to, the
buccal aperture, occurs an exceedingly minute circular
opening.
The skin is thick, comparatively firm-textured, and
quite opaque on the trunk; on the proboscis, it is
somewhat thinner and translucent. It consists of a cuticle, fig. 14,
a, which is hyaline, without striæ, and on the trunk exceed- •
ingly thin, so thin indeed as to be with difficulty
distinguished even under a strong magnifier; on the proboscis, it
is much thicker, fig. 15, a.
Underneath the cuticle extends the epithelium,
consisting of a layer of cylindric cells, in colour a pale
yellowish-green, 0.060""" long and 0.008mm broad at the base; they
become gradually narrower the nearer they approach the
cuticle, where they closely resemble a row of organ-pipes,
figs. 14, b; 15, b.
These long cylindric cells have, thickish walls, are
furnished with a large, dark-coloured nucleus, and a.
somewhat lighter nucleolus, both surrounded by finely granulated
protoplasma.
Immediately adjoining this epithelial layer, extends
the true cutis, consisting of a thick hyaline layer of
connective tissue, throughout which corpuscles of connective
tissue are abundantly dispersed, figs. 14, c; 15, c.
Underneath the layer of connective tissue extends the
muscular integument, composed of 3 layers: an outer
circular layer (the annular muscles), comparatively broad,
with strong, closely disposed muscular fibres, webbed together
by connective tissue, fig. 14, d; a medial layer (the long- .
itudinal muscles), broader than the outer annular muscles,
fig. 14, e, and with thicker fibres; and the inner annular
layer, which is exceedingly narrow, and with much
slenderer fibres than the two foregoing layers, fig. 14, /. The
inner annular layer is invested with peritoneum, having a
thin epithelial tunic, but whether vibratile — which is
probable — or without cilia, we could not determine.
On the proboscis,. the cylindrical cells are somewhat
shorter, and here the fibres of the muscular layer lie so
far apart as to give the integument a distinct tessellated
appearance.
On the inner surface of the skin, extending along
either side of the anterior extremity of the body, inside
the fore-mentioned fissure, are seen a series of round
openings (we counted 4 on each side),. surrounded by a circular
ridge, constituting a kind of sphincter round the opening,
which leads down to the bottom of the fissure, figs. 11, a;
12, a. Here (at the bottom of the. fissure) is placed a
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