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Til den indvendige Flade af Bindevævet er
Muskellaget fæstet. Det dannes af Tver- og Længdemuskler.
Tvermusklerne, Tab. IH, Fig. 26. a, a, ere temmelig
smale, men sammenbundne ved et hyalint, kalkfrit
Bindevæv til en sammenhængende Hud. J)e gaa fra den ene
Længdemuskel til den anden, stundom gaa de henimod
Midten af Længdemuskelen, hvor de da ophøre, aldrig gaa
de over Radialnerven eller Radialkarret. De kunne
følgelig ikke faa Benævnelsen Ringmuskler, da de ikke gaa
fortløbende rundt Legemet; men kunne langt bedre
benævnes Tvermuskler, da de udfylde 5 Felter, der
fremkomme ved Lærigdemu8klernes Anordning. Enhver saadan
Tvermuskel bestaar af en Mængde Muskelfibriller,
sammenbundne med Bindevæv.
Længdemusklerne ere 5. Tab. III, Fig. 26, e.
Enhver Muskel har en Bredde af 1,4™", er fæstet til Huden
ved en Mængde temmelig stærke Bindevævstraade, og
indtager Dyrets hele Længde. £)e aftage noget i Bredde,
saavel mod den forreste som bagerste Ende.. Fortil fæste
de sig paa Mundskivens yderste Rand, just ved Grunden
af en Tentakel, sende Fibre hen til den indre Del af
Mundskiven lige til Mundranden. Der, hvor Længdemusklerne
fæste sig paa Skiveranden, fremkommer, idet Fibrene vige
fra hverandre, et spidsvinklet Rum, der opfyldes af
Radialnerven og Karret. Bagtil fæste de sig paa Kloaken rundt
om dennes Aabning.
Længdemuskleraes Fibriller ere forgrenede og
ana-stomosere med hverandre. Hele Muskellaget er beklædt
af et flimrende Peritoneum, der foruden Epithelet bestaar
af et tyndt gjennemsigtigt Bindevæv, hvori sees enkelte
Muskelfibre.
I det tidligere beskrevne hyaline Bindevæv findes lejret
Kalklegemer af forskjellig Størrelse og Form og i forskjellig
Mængde. Disse Kalklegemer ligge noget under Epithellaget
og rage ikke op i dette. De fremtræde under 3 Former,
nemlig som Spikler, som Rosetter og som Net.
Spiklerne findes overalt; men i størst Mængde paa
Ryggen. De vise sig fornemmelig i to Størrelser, hvorfor
vi ville benævne dem de smaa og de store Spikler.
De smaa Spikler ere mere eller mindre krumbøjede, kun
enkeltvis ganske lige, have en Knude paa Midten, imedens
Enderne ere tildels afstumpede og finttakkede, Fig. 11, a.
De ligne meget de Spikler, som findes i Irpas Hud, kun
ere de meget mindre, 0.024*"" lange og 0,002"" tykke.
Disse smaa Spikler ligge dels spredte enkeltvis, saasom
paa Bugfladen, dels ere de sammenpakkede i Hobe, Fig.
11, Fig. 10, Fig. 22, dels indtage de et eller flere Lag.
To the inner surface of the connective tissue is
attached the muscular layer, composed of transverse and
longitudinal muscles.
The transverse muscles. Pl. Ill, fig. 26, a, a, are
somewhat slender, but form a continuous muscular
membrane, being webbed together by a layer of hyaline
connective tissue, without a trace of calcareous deposit. They
extend from one longitudinal muscle to the other, reaching
sometimes almost to the middle of those muscles, where
they terminate, never crossing the radial nerve or the radial
vessel. Hence, the appellation of ring, or annular, muscles
is incorrect, since they do not encircle the botfy; transverse
muscles would be a more appropriate term, occupying as
they do the 5 segments into which, by the arrangement of
the longitudinal muscles, the surface of the body is divided.
Each of these transverse muscles consists of numerous
muscular fibrils, webbed together by connective tissue.
The longitudinal muscles are 5 in number, Pl. Ill,
fig. 26, e. Each muscle has a breadth of 1.4"". is attached
to the integument by a multitude of comparatively strong
filaments of connective tissue, and protends throughout the
entire length of the animal. At both extremities they
experience a slight diminution in length. Anteriorly, they are
affixed to the extreme margin of the oral disk, each at the
, base of a tentacle, and send off fibres to the inner portion of
the disk, or rather to the edge of the oral orifice. These
fibres abruptly diverging, an acute-angled space, occupied
by the radial nerve and vessel," is marked off where the
longitudinal muscles issue from the margin of the oral disk.
Posteriorly, they are attached to the edge of the anal
opening.
The fibrils of the longitudinal muscles are ramous.
anastomosing one with the.other. Over the whole of the
muscular layer extends a ciliated peritoneum, which, in
common with the epithelium, consists of thin, translucent
connective tissue, in which may be discerned a few muscular
fibrils.
In the hyaline connective tissue, described above, are
calcareous corpuscles, varying alike in form, magnitude, and
number. These calcareous corpuscles lie a little beneath
the epithelial layer, none extending up into that division
of the integument. They are triform, viz. spicular,
flos-culous, and reticulate.
The spiculæ are everywhere met with, but in greatest
numbers on the back. The majority are of two
magnitudes, and hence may be conveniently designated the small
and the large spiculæ.
The small spiculæ are more or less inflexed, — but very
few, and those isolated, occur striotly rectilinear, — bearing
each a protuberance in the middle, and with obtuse or minutely
serrated extremities, fig. 11 a. They closely resemble the
spicules studding the integument in the genus Irpa,
but are very much smaller, measuring only 0.024"" in
length and 0.002"" in thickness. A threefold arrangement
characterises these diminutive spiculæ, some occurring isolated,
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