65 



Det tidligste Larvestadium, jeg har tumlet, er 

 af bildet Tab. IX, Fig. 7. Det svarer, livad Lem- 

 mernes Udvikling augaar. noget nær til det Tab. 

 VIII, Fig. 15 afbildede Stadium af Branchineckt, 

 men skiller sig mærkeligt derved, at de sammen- 

 satte Øine, der lios hint Stadium neppe endnu var 

 anlagte, her er meget tydeligt og omtrent ligesaa 

 vidt komne som paa det i andre Henseender meget 

 videre udviklede Stadium af Branchinecta, som er 

 fremstillet Fig. 17 paa samme Planrhe. Det s\'nes 

 altsaa som om disse Organer udvikles betydelig tid- 

 ligere hos nærværende Phyllopode. De 2 Par Fø- 

 lere og Kindbakkerne med sine Palper stemmer idet- 

 hele meget noie med samme hos det tilsvarende 

 Stadium af Branchinecta, alene med den Forskjel, at 

 den inderste af de 2 fra 2det Par Feieres Skaft ud- 

 gaaende, indadkrummede Fortsatser her er simpel, 

 ikke tvekloftet. Af Branchialfodder er der kun til- 

 stede 7 — 8 svage Anlæg i Form af simple Tvær- 

 vuLster til hver Side af Kropjien, som allerede viser 

 en tydelig Segmentering. Haleenden er noget ind- 

 snoret ved Basis og ender med 2 meget korte Lappe, 

 liver bærende en enkelt Borste. 



Den videre Udvikling foregaar paa en fuldkom- 

 men lignende Maade som hos Branchinecta, idet 

 Branchialfodderne suceessivt udvikles forfra bagtil, 

 medens 2det Par Folere og Mandibularfodderne grad- 

 vis reduceres. 



Forekomst og Levevis. 



Nærværende eiendommelige Phyllojiode er meget 

 almindelig overalt i Finmarken. Jeg har truffet 

 den paa folgende Lokaliteter: Bugo paa Sydsiden 

 af Var angerf jorden, Vadso, Fastlandet indenfor 

 Vardo paa mange Stedet, Vagge Tanafjord, Mehavn, 

 Hasvig paa Here Steder, Hammerfest ligesaa. Læn- 

 gere Syd paa Landet har jeg derimod aldrig stodt 

 paa den, og den synes saaledes hos os udelukkende 

 at være indskrænket til den arktiske Zone. Den 

 forekommer under lignende Forhold som Branchi- 

 necta paliidosa og ikke sjelden sammen med den. 

 Det er især i ganske grunde Smaatjern med mudret 

 Bund og som ud paa Sommeren delvis eller fuld- 

 stændig udtorres, at den paatræffes og her ofte i 

 enorme Mængder. Dog har jeg ogsaa af og til truf- 

 fet den i større og dybere Vande, f. Ex. i et Tjern 

 jiaa Hoideplateaiiet ved Vagge i Bunden af Tana- 

 f jorden, hvor den viste en vakker blaalig Farve- 

 tegning. Den svømmer ialmindelighed om i A'^andet 

 mere eller mindre nær Overtladen og med en ganske 

 jevn Fart, altid med Ryggen nedadvendt. Hanner 

 og Hunner træflFes meget ofte i ('opulation, og Han- 

 nen fastholder herunder Hunnen saa kraftigt med 

 sine Gribeantenner om Kjonsregionen, at det ikke 



— G. 0. Sårs: Fauna Norvegia'. 



The earliest larval stage that I have found is 

 figured on PI. IX, fig. 7. As regards the develop- 

 ment of the limbs, it answers to the stage oi Bratt- 

 chinecfa represented on PI. VIII, fig. 15, with the 

 remarkable difference that the compound eyes, which, 

 in that stadium, had scarcely commenced to appear, 

 are here very distinctly developed, and are about 

 as far advanced as in the, in other respects, much 

 further developed stadium of Branchinecta shown on 

 fig. 17 of the same plate. It tlierefore seems as if 

 these organs were developed much earlier in the 

 present Phyllopod. The two pairs of antennæ and 

 the mandibles with their palpi agree on the whole 

 very exactly with those organs in the corresjDonding 

 stage of Branchinecta, with the one difference, that 

 the inner of the two incurved processes starting 

 from the scape of the second pair of antennæ are 

 here simple, not bifid. There are only 7 or 8 slight 

 nidiments of Ijrancliial legs in the form of simple 

 transverse prominences on each side of the body, 

 which already shows distinct articulation. The ex- 

 tremity of the tail is somewhat constricted at the 

 base, and ends in two very short loljes, each carrying 

 a single bristle. 



Further development proceeds exactly as in 

 Branchinecta, the branchial legs developing succes- 

 sively from front to back, while the 2nd pair of 

 antennæ and the mandibular legs gradually di^ 

 minish. 



Occuvrence and Habits. 



This peculiar Phyllopod is very common over 

 the whole of Finmark. T have met with it in the 

 following localities: Bugo, on the south side of the 

 Varanger Fjord; Vadso; in many places on the 

 mainland south of Vardo; Vagge on Tana Fjord; 

 Mehavn; Hasvig in many places; also Hammerfest. 

 ()n tlie other hand, I have never come across it 

 further south, and it thus seems, in this country 

 (Norway) to be confined to the arctic zone. It is 

 found under tlie same conditions as, and not infre- 

 quently togetlier with Branchinecta jjalndosa. It is 

 especially in (juite shallow, small lakes with muddy 

 bottom, and which either partly or completely dry 

 up towards the end of the summer, that it is met 

 with, and there often in very great numbers. I have, 

 however, now and then also found it in larger, 

 deeper lakes, e. g. in a lake on the plateau at 

 Vagge, at the head of Tana Fjord, where it was of 

 a beautiful l)lue colour. It generalh' swims about 

 more or less near the .surface of the water at an 

 even rate, and with its back always turned down- 

 wards. Males and females are often found in copu- 

 lation, during which the male clasps the female so 

 firmly with its prehensile antennæ about the genital 



