88 



er et compliceret System af Hulruin, hvori Blodet 

 circulerer. Mellem disse Skikter af Skallen er ogsaa 

 Skalkjertelen beliggende. Denne sidste viser sig 

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

 beståa af en flere Gange slyngeforniigt l)ugtet Kanal, 

 der fortil delvis omgiver Insertionsareaen for Skal- 

 lens Lnkkemuskel, men hvis Hoveddel ligger umid- 

 delbart bag samme. Kanalens Udgangspunkt synes 

 at ligge lige over den sidstnævnte Area og omtrent 

 jiaa samme Sted ogsaa dens Ende ; men nogen skarp 

 Begrændsning mellem begge har jeg dog ikke knn- 

 net paavise, og det er muligt, at der her er en 

 direkte Kommnnikation, sa a at Kanalen i Virkelig- 

 heden danner et i sig selv tilbagegaaende Eor. Bag 

 Mnskelareaen danner Kanalen o ind i hverandre 

 liggende tnngeformige Slynger, der, om man forfol- 

 ger Kanalen fra dens tilsyneladende Udgangspunkt, 

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

 terste Slynge er den forst dannede, den yderste den 

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

 yderste Slynge er forbundet ved en smalt udlobende, 

 tungeformig Omboining, der strækker sig dorsalt 

 forover, og ender lige over Kanalens Udgangspunkt. 

 Den yderste og inderste Slynge gaar over i hinan- 

 den ved en lignende, men bredere r)mlioining, der 

 ligger mere. ventralt, lige nedenunder Mnskelareaen, 

 og her krydser den forreste Del af Kanalen. ( )ver- 

 alt viser Kanalens Konturer .sig uregelmæssigt 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 forlnddsvis liden Del af Skal- 

 eaviteten, livori det er frit sns])enderet, kun fæstet 

 helt fortil ved det ovenomtalte dorsale Ligament 

 og ved Skallens Lukkemnskel. Saavel den foran 

 som liagenfor liggende Del af Legemet er derfor 

 frit bevægelig, 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 

 bagenfor liggende og kan igjen deles i 2 under- 

 ordnede Afsnit, begrændsede fra hinanden oventil 

 ved en dyb Indbugtning. Den forreste Del er det 

 egentlige Hoved, den bager.ste det saakaldte Xakke- 

 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 forsto er af meget 

 ])et_ydelig Storrelse, den anden ganske kort. 



Af ydre Vedhæ.ng l)ærer Hovedet de 2 Par Folere 

 og fortsætter sig bagtil paa Undersiden i Overlæben. 



there is a complieated system of eavities in which 

 the blood eiroulates. Between these strata of the 

 shell, the shell-gland is also situated. This last proves, 

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

 sist of a twisted channel curled u]i in several windings, 

 which in front partially surround the area of inser- 

 tion of the shell's adductor muscle, but of whicli 

 the greater nundjer lie immediatidy Ijehind it. The 

 point of issue of the channel a])pears to lie just 

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

 aljout the same place; but I have not lieen able to 

 make out any sharp Ijonndary between the two. 

 and it is iiossible 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. Tiie outer- 

 mo.st and innermost coils run into one another with 

 a similar, but broader told, which is more ventral 

 in position, just Ijelow 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. visilde in its walls, 

 giving it a glandular a])pearance. 



The enclosed animal (see PI. XV. fig. 1) occu- 

 pies a comparatively small portion of the cavity of 

 the shell, within which it is tVeely suspended, being 

 attached only at the very front by tlie befn-e-men- 

 tioned dorsal ligament and hy the adductor muscle 

 of the shell. Both the anteriorly and the posteri- 

 orly situated part of the body can therefore l)e 

 freely moved, and several muscles may be seen 

 passing from the dorsal ligament both backwards 

 and forwards. The body permits of being naturallj' 

 divided into two ])rinci]ial sections, wliich form 

 more or less of an angle with one another, and whose 

 limits are indicated liy the dorsal ligament and the 

 adductor muscle. Tiie section situated in front of 

 these parts is mmdi 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 tVire part is tiie liead ])roper, the l)ack jiart, the 

 so-called cervical segment. Tiie extremely mobile 

 section situated behind the dorsal ligament and the 

 adductor musrle, is also ca])al)ii^ of being divided 

 into two, — the body ]iro])cr (trunk) and the caudal 

 part, the first of these being of very considerable 

 size, the second, i|uitc slioi't. 



Of tiie external appendages, the head carries 

 the 2 pairs of antenna', and is continued backwards 



