se lat ea eel 
21 
sidste er festet 4 sterke Torner, og fra Spidsen | single oval joint whose inner edge is straight, 
udgaar 2 lignende, hvoraf den inderste er lengst. 
Imellem Tornerne findes ogsaa her fine udadrettede 
Borster, medens Bersterne i Inderkanten er steerkt 
redncerede. 
Halegrenene (Fig. 12) er omtrent saa lange som 
de 2 sidste Bagkropssegmenter tilsammen og ialmin- 
delighed sterkt divergerende. De er af smal lineer 
Form, ganske lidt afsmalnende mod Enden og 
rundtom forsynede med en Rad af korte ucilierede 
Torner, der ved Spidsen antager Formen af sterkt 
forlengede Borster. Foruden disse findes langs 
Inderkanten en Rad af betydelig lengere og finere, 
tet cilierede Borster. 
Dyrets Farve er noget varierende fra meget 
bleg gulagtig til temmelig intens redbrun. De mest 
udpreget farvede Exemplarer har jeg observeret i 
vor arktiske Region. 
Beskrivelse af den slegtsmodne Han. 
Medens den endnu ikke slegtsmodne, skjondt 
forevrigt fuldt udvoxede Han (se Tab. II, Fig. 1) 
kun lidet skiller sig i sit Udseende fra Hunnen, er 
Forskjellen mellem de to Kjon i den slegtsmodne 
Tilstand saa skarpt udpreeget (se Tab. I, Fig. 1 og 
3), at man uden en noiere Undersogelse knapt en- 
gang skulde tro, at de tilhorte samme Art. Kjons- 
“forskjellen er udtrykt saavel i den hele Habitus 
som i Structuren af enkelte af Lemmerne, iseer de 
2 Par Felere, der er modificerede paa en meget lig- 
nende Maade som hos Hannerne af de fleste Amphi- 
poder. 
De storste Hanner, jeg har fundet, havde en 
Lengde af omtrent 12 mm.; men jeg har ved vor 
Sydkyst truffet Hanner af knapt mere end den halve 
Storrelse, skjondt fuldstendigt slegtsmodent ud- 
viklede. 
Legemets Form er (se Tab. I, Fig. 3) paafaldende 
smekrere end hos Hunnen, og navnlig er Rygskjol- 
det kjendelig smalere, seet fra Siden af elliptisk 
Form, med Hoiden neppe halvt saa stor som Leeng- 
den. Fremdeles er Bagkroppen noget lengere i 
Forhold til Forkroppen, og- dens forreste Afsnit 
kraftigere udviklet end hos Hunnen. Endelig giver 
de enormt forlengede Halegrene Dyret et fra Hun- 
nen meget afvigende Udseende. 
Minene er fuldkommen af samme Bygning som 
hos Hunnen, men synes noget storre og har det 
ydre Parti sterkere udvidet. 
whilst the outer edge is somewhat curved. To the 
last named 4 strong spines. are secured, and 2 simi- 
lar ones issue from the point, of which the inner- 
most one is the longest. Between the spines there 
are also found here fine bristles directed outwards, 
whilst the bristles on the inner margin are greatly 
reduced. 
The caudal rami (fig. 12) are about same 
length as the two last posterior segments of the 
body taken together, and are usually strongly diver- 
gent. They are of narrow, linear form, quite slightly 
narrowed towards the extremity, and furnished 
roundabout with a series of short non-ciliated spines, 
which at the tip assume the form of greatly pro- 
longed bristles. Besides these there are found, along 
the inner edge, a series of considerably longer and 
finer, closely ciliated bristles. 
The colour of the animal is somewhat variable, 
from very pale yellowish to pretty intense red- 
brown. I have observed the most distinguished co- 
loured. specimens in the Norwegian Arctic region. 
Description of the sexually ripe male. 
Whilst the not yet sexually ripe male, al- 
though in other respects fully developed (see PI. 
I, fig. 1), distinguishes itself in appearance only 
slightly from the female, the difference between the 
two sexes in the sexually ripe condition is so 
sharply defined (see PI. I, fig. 1 and 3), that without 
a close examination the observer would scarcely 
even believe that they pertained to the same species. 
The sexual difference is expressed both by the en- 
tire habitus, as well as in the structure of some of 
the appendages, especially the two pairs of antenna, 
which are modified in a very similar manner to 
that of the males of most Amphipods. 
The largest males I have found had a length 
of about 12 mm; but on our south coast I have met 
with males of scarcely more than half the size, 
although completely sexually developed. 
The form of the body (see Pl. I, fig. 3) is con- 
spicuously more slender than in the female, and the 
carapace, especially, is perceptibly narrower; viewed 
from the side the shape is elliptical, the height 
being scarcely half so great as the length. Further, 
the posterior division of the body is somewhat 
longer in relation to the anterior one, and its fore- 
most section more powerfully developed than in the 
female. Finally, the enormously prolonged caudal 
rami impart to the animal a very different appear- 
ance from the female. 
The eyes are of exactly the same structure as 
in the female, but appear to be somewhat larger, 
and have the outer portion more dilated. 
