er et compliceret System af Hulrum, hvori Blodet 
cireulerer. Mellem disse Skikter af Skallen er ogsaa 
Skalkjertelen beliggende. Denne sidste viser sig 
ved nermere Undersogelse (se Tab. XV, Fig. 14) at 
bestaa af en flere Gange slyngeformigt bugtet Kanal, 
der fortil delvis omgiver Insertionsareaen for Skal- 
lens Lukkemuskel, men hvis Hoveddel ligger umid- 
delbart bag samme. Kanalens Udgangspunkt synes 
at ligge lige over den sidstneynte Area og omtrent 
paa samme Sted ogsaa dens Ende; men nogen skarp 
Begreendsning mellem begge har jeg dog ikke kun- 
net paavise, og det er muligt, at der her er en 
direkte Kommunikation, saa at Kanalen i Virkelig- 
heden danner et i sig selv tilbagegaaende Ror. Bag 
Muskelareaen danner Kanalen. 3 ind i hverandre 
liggende tungeformige Slynger, der, om man forfol- 
ger Kanalen fra dens tilsyneladende Udgangspunkt, 
folger paa hinanden i en saadan Orden, at den mid- 
terste Slynge er den forst dannede, den yderste den 
2den, og den inderste den 3die. Den midterste og 
yderste Slynge er forbundet ved en smalt udlobende, 
tungeformig Omboining, der strekker sig dorsalt 
forover, og ender lige over Kanalens Udgangspunkt. 
Den yderste og inderste Slynge gaar over i hinan- 
den ved en lignende, men bredere Omboining, der 
ligger mere ventralt, lige nedenunder Muskelareaen, 
og her krydser den forreste Del af Kanalen. Over- 
alt viser Kanalens Konturer sig uregelmessigt tak- 
kede, og i dens Vegge sees spredte Cellekjerner, 
givende den et glandulost Udseende. 
Det i Skallen indesluttede Dyr (se Tab. XV, 
Fig. 1) indtager en forholdsvis liden Del af Skal- 
caviteten, hvori det er frit suspenderet, kun festet 
helt fortil ved det ovenomtalte dorsale Ligament 
og ved Skallens Lukkemuskel. Saavel den foran 
som bagenfor liggende Del af Legemet er derfor 
frit beveegelig, og flere Muskler sees ogsaa at pas- 
sere fra det dorsale Ligament saavel fortil som 
bagtil. Legemet lader sig naturligt dele i 2 Hoved- 
afsnit, der med hinanden danner en storre eller min- 
dre Vinkel, og hvis Begrendsning antydes ved det 
dorsale Ligament og Lukkemuskelen. Det foran 
disse Dele liggende Afsnit er meget mindre end det 
bagenfor liggende og kan igjen deles i 2 under- 
ordnede Afsnit, begreendsede fra hinanden oventil 
ved en dyb Indbugtning. Den forreste Del er det 
egentlige Hoved, den bagerste det saakaldte Nakke- 
segment. Det bagenfor det dorsale Ligament og 
Lukkemuskelen liggende, seerdeles bevegelige Afsnit 
lader sig ligeledes dele i 2, den egentlige Krop 
(truncus) og Haledelen, hvoraf den forste er af meget 
betydelig Storrelse, den anden ganske kort. 
Af ydre Vedheeng berer Hovedet de 2 Par Folere 
og fortsetter sig bagtil paa Undersiden i Overleben. 
88 
there is a complicated system of cavities in which 
the blood circulates. Between these strata of the 
shell, the shell-gland is also situated. This last proves, 
on a close examination (see Pl. XV, fig. 14) to con- 
sist of a twisted channel curled up in several windings, 
which in front partially surround the area of inser- 
tion of the shell’s adductor muscle, but of which 
the greater number lie immediately behind it. The 
point of issue of the channel appears to lie just 
over the above-mentioned area, and its end also at 
about the same place; but I have not been able to 
make out any sharp boundary between the two, 
and it is possible that there is here a direct commu- 
nication, so that the channel forms in reality a tube 
running back into itself. Behind the muscular area, 
the channel forms 3 linguiform coils lying within 
one another, which, if the course of the channel be 
traced from its apparent origin, so follow one an- 
other, that the middle coil is the first formed, the 
outermost one, the second, and the innermost, the 
third. The middle and outermost coils are con- 
nected by a narrowly projecting, lingular fold, 
which extends forwards dorsally, and ends just 
above the starting-point of the channel. The outer- 
most and. innermost coils run into one another with 
a similar, but broader fold, which is more ventral 
in position, just below the muscular area, and here 
crosses the front part of the channel. The outline 
of the channel is throughout irregularly jagged, 
and scattered cell-nuclei are visible in its walls, 
giving it a glandular appearance. 
The enclosed animal (see Pl. XV, fig. 1) oceu- 
pies a comparatively small portion of the cavity of 
the shell, within which it is freely suspended, being 
attached only at the very front by the before-men- 
tioned dorsal ligament and by the adductor muscle 
of the shell. Both the anteriorly and the posteri- 
orly situated part of the body can therefore be 
freely moved, and several muscles may be seen 
passing from the dorsal ligament both backwards 
and forwards. The body permits of being naturally 
divided into two principal sections, which form 
more or less of an angle with one another, and whose 
limits are indicated by the dorsal ligament and the 
adductor muscle. The section situated in front of 
these parts is much smaller than that lying behind, 
and can be again divided into 2 sub-sections, sepa- 
rated from one another above by a deep hollow. 
The fore part is the head proper, the back part, the 
so-called cervical segment. The extremely mobile 
section situated behind the dorsal ligament and the 
adductor muscle, is also capable of being divided 
into two, — the body proper (trunk) and the caudal 
part, the first of these being of very considerable 
size, the second, quite short. 
Of the external appendages, the head carries 
the 2 pairs of antenne, and is continued backwards 
