56 



af Himkjøn, sker der en end yderligere Reduktion 

 af disse Følere, hvorved de aiitager det for Hunnen 

 characteristiske Udseende af 2 simple triangulære 

 FKge. Hos Hannen omformes Ydergrenen til Grribe- 

 kloen, og Indergrenen persisterer som det lille knude- 

 formige Frenisi)ring ved Enden af Basaldelen, inden- 

 denfor Kloens Udspring. 



Forekomst og Levevis. 



Nærværende Phyllopode synes at forekomme 

 meget ahnindelig, i Øst-Finmarken, hvor jeg har 

 tåget den paa flere Steder i stor Mængde; saaledes 

 i et lidet grundt Tjern ved Mehavn, hvor den fand- 

 tes sammen med Polyartemia forcipata, i et lignende 

 Tjern ved Vardo, og i flere Smaatjern og grunde 

 Damme paa Fastlandet Øst af Vardo. Af Prof. 

 Lilljehorg er den desuden tåget ved Nordkap. I 

 Vest-Finmarken har jeg derimod ikke observeret 

 den, ligesaalidt som nogetsteds i Nordland. Mærke- 

 ligt nok optræder den igjen langt sydligere i Lan- 

 det, nemlig paa Dovres Hoideplateau, hvor jeg har 

 tåget den meget almindelig i grunde Damme saavel 

 ved Kongsvold som ved Jerkin. Denne isolerede 

 Forekomst saa langt Syd paa kan kun forklares 

 ]jaa den Maade, at nærværende Phyllopode før i 

 Tiden, da Klimatet var mere arktiskt, har været 

 udbredt over hele vort Land, ogsaa i Lavlandet, 

 men derpaa, efterhvert som Klimatet forandrede sig, 

 liar trukket sig tilbage nordpaa og tillige til Hoide- 

 plateauerne, hvor de klimatiske Forhold mere lig- 

 nede de oprindelige ; med andre Ord : den er her S^'^d 

 i Landet at betragte som en saakaldt «relict» Form, 

 en Levning fra den arktiske Fauna, der for i Tiden 

 var udbredt over vort hele Land. 



Da de Smaatjern og Damme, hvori den lever, 

 regelmæssigt udtorres mod Shitningen af Sommeren, 

 os væsentlie kiin skvlder sin Tilbliven Snesmeltnin- 

 gen paa Forsommeren, er denne Forms Levetid kun 

 ind.skrænket til nogle faa Maaneder af Aaret. I 

 Lobet af forholdsvis kort Tid har den imidlertid 

 gjennemgaaet sin Udvikling, og derefter gaar For- 

 plantningen hurtigt for sig. De i Ægsækken inde- 

 holdte Æg, Ijliver, som anfort, altid omgivne med en 

 meget ty\i Skal og er aabenbart alle beregnede paa 

 at overvintre, for til den følgende Sommer at ud- 

 vikle sig til en ny Greneration. Arten er saaledes 

 for hvert Aar kun repræsenteret ved en enkelt Ge- 

 neration. Æggene atsættes i Mudret paa Bunden 

 af Dammen, og da denne Afsætning afÆg foregaar 

 gjentagne Gange af hvert Hunindivid, vil der snart 

 ophobe sig en anseelig Mængde af Æg, der vil sikre 

 Artens Tilværelse paa de Steder, der er gunstige 

 for dens Trivsel. Det er forst ved Midsommertid, 



with no bristles whatever. If the young one is 

 destined to be of the female sex, a still further re- 

 duction of these antennæ takes jilace, whereby thej^ 

 assume the appearance, characteristic of the females, 

 of 2 simple triangular flaps. Li the male the outer 

 ramus is transformed into a prehensile claw, while 

 the inner ramus becomes the small nodiform pro- 

 jection at the end of the basal part, inside the root 

 of the claw. 



Occurence and Habits. 



The present Pliyllo]iod seems to occur very ge- 

 nerally in East Finmark, where I have found it in 

 many places in great numbers, for instance, in a 

 little, shallow lake at Mehavn, where it was found 

 together with Poh/arfemia forcipata: in a similar 

 lake at Vardo, and in several small lakes and 

 shallow ponds on the mainland east of Vardø. It 

 has also been found by Prof. Lill jeborg at the North 

 Cape. In West Finmark, on the other hand, I have 

 not observed it, nor yet anywhere in Nordland. 

 Curiously enough, it appears again much farther 

 south, namely on the high plateau of the Dovre 

 Mountains, where I foiind it very plentiful in shal- 

 low ponds both at Kongsvold and Jerkin. This 

 isolated occurrence so far south can only be ac- 

 counted for by the supposition that formerly, when 

 the climate was more arctic, this Phyllopod was 

 distributed over the whole of our land (Norway), 

 lowlands as well as highlands, but that, as the cli- 

 mate changed, they have withdrawn to the north 

 and the high plateaus, where the climatic conditions 

 more resemble those originally prevailing; in other 

 words, here in the south of the country, it must be 

 regarded as a so-called «relict» form, a vestige of 

 the arctic fauna which was formerly distributed 

 over the whole country. 



As the small lakes and ponds in which it lives 

 drv up periodically towards the end of the summer, 

 and owe their existence chiefly to the melting of 

 the snow in the spring, the life-time of this form 

 is limited to only a few months of the year. In 

 the coTirse of a comparatively short time, however, 

 it has passed through its developmental course, and 

 propagation then proceeds rapidly. As already stated, 

 the eggs in the ovisac always become surrounded by 

 a very thick shell, and are evidently calculated to 

 stand the winter, and in the ensuing summer to 

 develop into a new generation. The species is thus 

 represented every year only by a single generation. 

 The eggs are deposited in the mud at the bottom 

 of the pond, and as this deposition of eggs is re- 

 peated several times by each female, a considerable 

 number of eggs is soon amassed, wliich ensures the 

 existence of the species in those places that are favor- 

 able to its well-being. It is not until Midsummer 



