88 



er et complieeret System af Hulnim, hvori Blodet 

 circixlerer. Mellem disse Slvikter af Skallen er ogsaa 

 Skalkjertelen beliggende. Denne sidste viser sig 

 ved nærmere Undersogelse (se Tab. XV, Fig. 14) at 

 beståa af en flere Gange slyngeformigt bngtet Kanal, 

 der fortil delvis omgiver Insertionsareaen for Skal- 

 lens Lukkemuskel, men hvis Hoveddel ligger nmid- 

 delbart bag samme. Kanalens Udgangspnnkt synes 

 at ligge lige over den sidstnævnte Area og omtrent 

 paa samme Sted ogsaa dens Ende; men nogen .skarp 

 Begrændsning 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 

 Mnskelareaen danner Kanalen 3 ind i hverandre 

 liggende tungeformige Slynger, der, om man forfol- 

 ger Kanalen fra dens tilsyneladende Udgangsjiunkt, 

 følger paa hinanden i en saadan Orden, at den mid- 

 terste Slynge er den forst dannede, den ydei'ste den 

 2den, og den inder.ste den oåie. Den midterste og 

 yderste Slynge er forbundet ved en smalt udlobende, 

 tungeformig Omboining, der strækker sig dorsalt 

 forover, og ender lige over Kanalens Udgangspnnkt. 

 Den yderste og inderste Slynge gaar over i hinan- 

 den ved en lignende, men bredere Omboining, der 

 ligger mere ventralt, lige nedeniinder Mnskelareaen, 

 og her kiydser den forreste Del af Kanalen. Over- 

 alt viser Kanalens Kontiirer sig nregelmæssigt tak- 

 kede, og i dens Vægge 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 snsjienderet, knn fæstet 

 helt fortil ved det ovenomtalte dorsale Ligament 

 og ved Skallens Lukkemuskel. Saavel den foran 

 som bagenfor liggende Del af Legemet er, derfor 

 frit lievægelig, 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 Begrændsning antydes ved det 

 dorsale Ligament og Lukkemuskelen. Det foran 

 disse Dele liggende Afsnit er meget mindre end det 

 liagenfor liggende og kan igjen deles i 2 under- 

 ordnede Afsnit, begrændsede fra hinanden oventil 

 ved en dyb Lidbugtning. Den forreste Del er det 

 egentlige Hoved, den bagerste det saakaldte Nakke- 

 segment. Det bagenfor det dorsale Ligament og 

 Lukkemuskelen liggende, særdeles bevægelige Afsnit 

 lader sig ligeledes dele i 2, den egentlige Krop 

 (truncus) og Haledelen, hvoraf den forste er af meget 

 betydelig Størrelse, den anden ganske kort. 



Af ydre Vedhæng bærer Hovedet de 2 Par Folere 

 og fortsætter sig bagtil paa Undersiden i Overlæben. 



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 jiroves, 

 on a close examination (see PI. XV, fig. 14) to con- 

 sist of a twisted chaimel curled up in several windings, 

 which in front partially surround the area of inser- 

 tion of the shell's adductor muscle, l>ut of which 

 the greater number lie immediately behind it. The 

 point of issue of tlie cliannel appears to lie just 

 over the above-mentioned area, and its end also at 

 about the same place; but I have not l)een able to 

 make (nit any sharp lioi^ndary between the two, 

 and it is jiossible 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 witliin 

 one another, which, if the course of the channel be 

 traced from its apparent origin, so follow one an- 

 otlier, that the middle coil is tlie first formed, the 

 outermost one, the second, and the innermo.st, the 

 third. The middle and outermost coils are con- 

 nected by a narrowl\' 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 In-oader fold, which is more ventral 

 in pcsition, just below the muscular area, and here 

 crosses the front ])art 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 PI. XV. fig. 1^ occu- 

 pies a comparatively small portion of the cavity of 

 the shell, within which it is freely suspended, being 

 attacheil only at the very front by the Ijefore-men- 

 tioned dorsal ligament and by tlie 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 l)oth backwards 

 and forwards. Tlie l>ody i)ermits of being naturally 

 divided into two ])rinci])al 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 i)ro]ier, 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 ])roper (trunk) and the caudal 

 part, the first of these being of very considerable 

 size, the second, ((uite short. 



(^f the external appendages, the head carries 

 the 2 ])airs of antenna^, and is continm.'d backwards 



