43 



Det paa Hovedet folgende Kropsafsnit, Midt- 

 kroppen eller Truncus, er fortil omtrent af Hovedets 

 Brede og lidt nedtrykt, men afsinalnes lidt i sin 

 bagersteDel. Det er sammensat af 11 jiaa binandon 

 følgende korte og ensformigt udviklede Segmenter, 

 livoraf ethvert bærer et Par Branchialfodder. Disse 

 sidste følger med regelmæssige korte Mellemrum 

 efter binanden, dannende med sine forskjellige Lap- 

 per og talrige Borster til liver Side en bred Bræmme. 

 Herved fremkommer langs Midtkroppens Underside 

 en af samtlige Branchialfodder begrændset kanal- 

 agtig Fordjdjning, der gradvis tiltager noget i Brede 

 fortil, hvor den stoder op mod Mnndregionen. 



Bagkroppen eller Halen er overordentlig slank, 

 betydelig smalere end Midtkroppen, og af regelmæs- 

 sig cylindrisk Form. Den ndgjor kjendeligt mere 

 end Halvdelen af Legemets Totallængde, og er sam- 

 mensat af 'J Segmenter foruden Halegrenene. Af 

 disse Segmenter er de '2 forreste kun i den dorsale 

 Del tydeligt sondrede, medens de ventralt gaar over 

 i binanden og danner her Udspringet for de ydre 

 Kjonsvedhæng. Disse 2 forste Segmenter af Halen 

 vil derfor passende kunne benævnes: «Kjonsringene >. 

 Hos Hunnen er det forreste af disse Segmenter noget 

 opsvulmet fortil, og det bagerste danner nedentil, 

 ved Basis af Ægbeholderen, 2 rundagtige Fremspring 

 der navnlig er meget tydeligt fremtrædende, naar 

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

 Tab. Vni, Fig. 11). De folgende 5 Segmenter er 

 alle af ens Udseende og ogsaa af tilnærmelsesvis 

 samme Storrelse, simpelt cylindriske, med Længden 

 betydelig større end Breden. Næstsidste Segment 

 er deriniod 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 Indbugtning. Til hver Side 

 af denne, og adskilte i Midten ved et større M(dlem- 

 rum, er fæstet de smalt laneetformige Halegrene, 

 der maaske, i Lighed med den saakaldte Furca hos 

 Copepoderne, kan betragtes som frendvomne ved Klov- 

 ningen af et terminalt Segment, num som dog vel 

 uorrectest vil kunne beskrives som et Bar omformede 

 Lemmer. 



Hunnens Længde gaar op til IS mm. Hannen 

 er i llcgelen kjendelig større og opnaar ofte en 

 Længde af indtil 2i'> mm. Begge Kjon er dcsuden let 

 kjendelige ved den meget forskjellige Udvikling af 

 2det Par Følere, samt ved Beskatfenheden af de 

 ydre Kjonsvedliæng. Disse vil passende kunne be- 

 skrives paa dette Sted. 



maxillæ issne ventrally from the cervical seg- 

 ment. 



The division of the body that succeeds the 

 head, the mesosome or truncus, is about 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. Tliese last follow after each other at regular 

 short intervals, forming with their varioiis lobes 

 and numerous bristles a broad fringe on either 

 side. In this wa}' 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 extraordinarilj' slen- 

 der, considerably narrower than the mesosome, and 

 of regular cylindrical shape. It occupies appreciably, 

 more than half tlie entire length of the body, 

 and is composed of 9 segments besides the caudal 

 rami. Of tliese segments, the 2 foremost ones 

 are only distinctly separated in the dorsal part, 

 whilst they ventrally pass over into each other, and 

 form here the origin of tlie outer sexual appendages. 

 These 2 tii'st segments of tlie tail ma^-, 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 prominences, 

 which are, especially, very distinctly prominent when 

 the animal is viewed from above or from below (see 

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

 5 segments have all a uniform appearance, and are 

 also of approximately the same size, plain cylin- 

 drical, with the length considerabl}^ greater tlian 

 the breadtli. The penultimate segment is, on the 

 contrary, considerably longer than the others, while, 

 on the other hand, the last is ver}' 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 tlie posterior 

 edge shows a quite faint sinus. On either side 

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

 gish interval, tlie luirrow lanceolate caudal rami 

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

 furca in the Copepods, may be considered as pro- 

 duced by the s])litting of a terminal segment, but 

 which, however, probably more correctly may be 

 described as a pair of transformed ajipendages. 



Tlie length of the female reaches up to 18 ni. ni. 

 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 ditferent 

 development of the 2nd pair of antennæ. and by 

 the character of the outer sexual ajipendages. These 

 may be conveniently described here. 



