43 



Det paa Hovedet følgende Kropsafsnit, Midt- 

 kroppen eller Truncus, er fortil omtrent af Hovedets 

 Brede og lidt nedtrykt, men afsmalnes lidt i sin 

 bagersteDel. Det er sammensat af 11 paa hinanden 

 følgende korte og ensformigt udviklede Segmenter, 

 hvoraf ethvert bærer et Par Branchialfodder. Disse 

 sidste folger med regelmæssige korte Mellemriim 

 efter liinanden, dannende med sine forskjellige Lap- 

 per og talrige Børster til liver Side en bred Bræmme. 

 Herved fremkommer langs Midtkroppens Underside 

 en af samtlige Branchialfodder begrændset kanal- 

 agtig Fordybning, der gradvis tiltager noget i Brede 

 fortil, hvor den stoder op mod Mundregiouen. 



Bagkroppeu eller Halen er overordentlig slank, 

 betydelig smalere end Midtkroppen, og af regelmæs- 

 sig cylindrisk Form. Den udgjør kjendeligt mere 

 end Halvdelen af Legemets Totallængde, og er sam- 

 mensat af 9 Segmenter foruden Halegrenene. Af 

 disse Segmenter er de '2 forreste kun i den dorsale 

 Del tydeligt sondrede, medens de ventralt gaar over 

 i hinanden og danner her Udspringet for de ydre 

 Kjonsvedhæng. Disse 2 forste Segmenter af Halen 

 vil derfor passende kunne benævnes: < Kjønsringene». 

 Hos Hunnen er det forreste af disse Segmenter noget 

 opsvuhnet fortil, og det bagerste dan)ier nedentil, 

 ved Basis af Ægbeliolderen, 2 rundagtige Fremspring^ 

 der navnlig er meget tydeligt fremtrædende, naar 

 Dyret sees ovenfra eller nedenfra (se Tab. VI, Fig. 4, 

 Tab. Vni, Fig. li'). De følgende 5 Segmenter er 

 alle af ens Udseende og ogsaa af tilnærmelsesvis 

 samme Størrelse, simpelt cjdindriske, med Længden 

 betydelig større end Breden. Næstsidste Segment 

 er derimod betydelig længere end de ovrige, og sidste 

 omvendt meget kort, neppe mere end halvt saa langt 

 som næstsidste. Det er (se Tab. VI, Fig. 10) tvært 

 afkuttet i Enden og viser i Midten af den bagre 

 Kant en ganske svag Indbugtuing. Til hver Side 

 af denne, og adskilte i Midten ved et større Mellem- 

 rura, er fæstet de smalt lancetformige Halegrene, 

 der maaske, i Liglied med den saakaldte Fnrea hos 

 Copepoderne, kan betragtes som fremkomne ved Klov- 

 ningen af et terminalt Segment, men som dog vel 

 correctest vil kunne beskrives som et Par omformede 

 Lemmer. 



Hunnens Længde gaar op til 18 mm. Hannen 

 er i Eegelen kj endelig større og opnaar ofte en 

 Længde af indtil 23 mm. Begge Kjøn er desuden let 

 kjendelige ved den meget forskjellige Udvikling af 

 2det Par Følere, samt ved Beskatfenhedeu af de 

 ydre Kjonsvedhæng. Disse vil passende kunne be- 

 skrives paa dette Sted. 



maxillæ issue ventrall}' from the cervical seg- 

 ment. 



The division of the body tliat succeeds the 

 head, the mesosome or truncus, is aboiit same 

 breadth in front as the head, and a little flattened, 

 but narrows a little in its backmost part. It is 

 composed of 11 short and uniformly developed seg- 

 ments, of which each carries a pair of branchial 

 feet. These last follow after each other at regular 

 short intervals, forming with their various lobes 

 and numerous bristles a broad fringe on either 

 side. In this way there is produced along the un- 

 derside of the mesosome a canalular cavity, borde- 

 red by all the branchial feet, which gradually in- 

 creases somewhat in breadth in front, where it 

 joins up to the oral region. 



The metasome or tail is extraordinarily slen- 

 der, considerably narrower than the mesosome, and 

 of regular cylindrical shape. It occupies appreciably, 

 more than half the entire length of the body, 

 and is composed of 9 segments besides the caudal 

 rami. Of these segments, the 2 foremost ones 

 are only distinct^ separated in the dorsal part, 

 whilst they ventrally pass over into each other, and 

 form here the origin of the outer sexual appendages. 

 These 2 first segments of the tail may, therefore, sui- 

 tably be named «the sexual segments». In the female 

 the foremost of these segments is somewhat swollen 

 in front; and the backmost forms downwards, at 

 the base of the marsupium, 2 roundish pi'ominences, 

 which are, especially, very distinct!}^ prominent when 

 the animal is viewed from above or from below (see 

 PI. VI, fig. 4, PI. VIII, fig. 11). The succeeding 

 5 segments have all a iiniform appearance, and are 

 also of approximately the same size, plain cylin- 

 drical, with the length considerably greater than 

 the breadth. The penultimate segment is, on the 

 contrary, considerably longer than the others, while, 

 on the other hand, the last is very short, scarcely 

 more than half as long as the penultimate one. It 

 is (see PI. VI, fig. 10) transversally truncated at 

 the extremity, and in the middle of the ])osteripr 

 edge shows a quite faint sinus. On either side 

 of this, and se]iarated in the middle by a lar- 

 gish interval, the narrow lanceolate caudal rami 

 are attached, which, perhaps, like the so-called 

 furca in the Copepods, may be considered as pro- 

 duced by the splitting of a terminal segment, but 

 which, however, probably more correctly may be 

 described as a pair of transformed appendages. 



The length of the female reaches up to 18 m. m. 

 The male is, as a rule, appreciably larger, and fre- 

 quently attains a length of 23 m. m. Both sexes 

 are, further, easily recognizable by the very different 

 development of the 2nd pair of antennæ, and by 

 the character of the outer sexual appendages. These 

 may lie conveniently described here. 



