96 



dele som liver udmunder med en kort Udforselsgang 

 noget lateralt i Tarmens forreste Del, og i sin Peri- 

 pheri er delt i talrige bugtede Blindsække, ialminde- 

 ligked fyldte med et intenst gultfarvet Stof. Hvert 

 Organ ndsender nedad en Sidegren, der i Hovedets 

 ventrale Del, iimiddelVjart foran Basis af Overlæben, 

 oploser sig i flere uregelmæssige Lappe. Hoved- 

 massen af Organet Ugger dog dorsalt, hvor det 

 sammen med det tilsvarende Organ paa den anden 

 Side danner en tils3-neladende sammenhængende 

 Kalot over Tai'niens forreste Del (se Fig. 2 og 3). 



Circulationsapparatet. — Hjertet (.^e Tab. XV, 

 Fig. 1) er beliggende ovenover Tarmen i den forre- 

 ste Del af Truncus, strækkende sig fortil ind i 

 Nakkesegmentet, bagtil ind i det 4de fodbærende 

 Segment. Det bar Formen af et fortil noget videre 

 cylindriskt Ror, aabent i begge Ender, og desnden 

 fors_ynet til hver Side med 4 tydelige Spaltaabninger, 



1 Par for Nakkesegmentet, de 3 ovrige Par for de 

 3 forreste Segmenter af Tranens. Af nogen virke- 

 lige Blodkar har jeg ikke knnnet tinde noget Spor; 

 men Blodet folger dog under sin Circulation i Lege- 

 met visse meget bestemte Baner. Da Blodlegemerne 

 er meget tydelige, er det ikke saa vanskeligt paa 

 tilstrækkelig gjennemsigtige levende Exemplarer at 

 studere de væsentligste Træk af Circulationen, og 

 jeg skal i det følgende i Korthed beskrive samme, 

 saaledes som jeg har troet at finde den ved gjen- 

 tagne omhyggelige Undersogelser. Fra den bagre 

 Del af Legemet kommer en stærk Strom af Blod, 

 der folger Ilygsiden af Truncus og passerer direkte 

 ind i Hjertet gjennem dettes bagre Aabning. Ved 

 Hjertets Systole lukkes denne Aabning, saavelsom 

 de laterale Spaltaabninger, og Blodet stodes med 

 stor Kraft ud af Hjertets forreste Ende. En Del 

 af den saaledes af Hjertet udkomne Blodmasse pas- 

 serer direkte ind i den forreste Del af Legemet og 

 forsj-ner Hovedet med dets forskjellige Vedhæng 

 med Blod. En anden Blodstrøm boier ])lndselig om 

 under Hjertet og lober bagover, umiddelbart neden- 

 for den tilførende dorsale Blodstrøm, lige til Hale- 

 delen, hvor den S3'nes at boie om paa Bagsiden af 

 Dyret for at forsyne Branchialfødderne med Blod. 

 En 3die betydelig Del af den fra Hjertet udstodte 

 Blodmasse passerer til hver Side mod Skallens Lukke- 

 muskel, hvor den i Omkredsen af Muskelareaen 

 trænger ind i selve Skallen. Herfra fordeles Blodet 

 rundt om i de to Valvler, idet det i forskjellige Baner 

 gjennemstrommer det complicerede System af Hul- 

 rum, der, som ovenfor anført, findes mellem disses 



2 Lameller. Efrerat have circuleret i Skallen sam- 

 ler Blodet sig lidt efter lidt i 2 dorsale Hoved- 

 strømme, der lober langs Rygkanten af Skallen, 

 en ganske kort forreste, og en betydelig længere 



is there also situated in the head. As in Lepidunis, 

 this organ consists of two symmetrical halves each 

 opening by a short excretory duct somewliat later- 

 all\^ in the anterior j)art of the intestine, and 

 divided in its periphery into numerous cæca, gene- 

 rally filled with a substance of an intense yellow 

 colour. Each organ sends down a lateral branch 

 which is resolved into several irregular lobes in the 

 ventral part of the liead immediately in front of the 

 base of the lalnnim. The great bulk of the organ, 

 however, is situated dorsally, where, together with 

 the corre.sponding organ on the otlier side, it foi'ms 

 an a])parently continuous cap over the anterior part 

 of the intestine (see figs. 2 and 3). 



Circulatory System. — The heart (see PI. XV. 

 fig. 1) is situated aliove the intestine in the anterior 

 part of the trunk, extending forwards into the cer- 

 vical segment, and Ijaekwards into the 4th pediger- 

 ous segment. It has the shape of a C3dindiical 

 tube, rather wider in front, and open at both ends, 

 and also furnished at each side with 4 distinct ostia, 

 one pair for the cervical segment, the other 3 for 

 the 3 foremost segments of the trank. I have been 

 unable to find any trace of actual blood-vessels, but 

 during its circulation through the bod}', the blood 

 follows certain fixed courses. As the corpuscles are 

 very distinct, it is not difficult in sufficiently tran- 

 sparent living specimens to study the principal fea- 

 tures of the circulation, and I will here briefly 

 describe them as I have found them bv' repeated 

 careful investigations to be. From the hind part of 

 the body comes a strong stream of blood keeping 

 to the dorsal side of the trunk, and ])assing directly 

 into the heart through its posterior aperture. Tliis 

 aperture, as well as the lateral ostia, is closed h\ 

 the hearts sj'stole, and the blood is ejected with 

 great force from the anterior end of the heart. A 

 portion of the (|uantit\- of blood thus issuing from 

 the heart, jiasses directly into the anterior part of 

 the body, and supplies the head and its various 

 appendages with blood. Another stream of blood 

 tarns suddenly below the heart and flows back- 

 wards immediately below the aflferent dorsal stream 

 right lip to the caudal ])art, where it appears to 

 turn to the ventral side of the animal, in order to 

 supply the branchial legs with blood. A third con- 

 siderable part of the quantitj' of blood ejected from 

 the heart, passes on botli sides towards the adductor 

 muscle of the shell, where, w'ithin tlie circumference 

 of the muscular area, it forces its wav into the 

 shell itself. From this the blood is distrilmted over 

 the two valves, flowing by various courses through 

 the complicated system of cavities which, as .stated 

 above, is found between their 2 lamellæ. After 

 having circulated in the sliell, the blood gradually 

 collects in two principal, dorsal streams which run 

 along tlie dorsal edge of tlie shell, one (piite short 



