56 



at' Huukjon, sker der en end yderligere Iteduktioii 

 af disse Folere, hvorved de aiitager det for Hunnen 

 fharafteristiske Udseende af 2 simple triangulære 

 Flige. Hos Hannen omformes Ydergrenen til (Iribe- 

 kloen, oglndergrenen per.sisterer som det lille knude- 

 formige Fremspring ved Enden af Hasaldelen, inden- 

 denfor Kloens Udsjning. 



Forekomst og Levevis. 



Nærværende Pliyllopode synes at forekomme 

 meget almindelig, 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 Foh/arfemia forcipata, i et lignende 

 Tjern ved Vai-do, og i Uere Smaatjern og grunde 

 Damme paa Fastlandet Øst af Vardo. Af Prof. 

 Lilljeborg er den desuden tåget ved Nordkap. I 

 Vest-Finmarken har jeg derimod ikke oliserA'eret 

 den, ligesaalidt som nogetsteds i Nordland. Mærke- 

 ligt nok optræder den igjen langt sydligere i Lan- 

 det, nemlig ])aa Dovres Hoide])lateau, livor jeg liar 

 faget den meget almindelig i grunde Damme saavel 

 ved Kongsvold som ved Jerkin. Denne isolerede 

 Forekomst saa langt Syd paa kan kun forklares 

 ])aa den Maade, at nærværende Phyllo]iode for i 

 Tiden, da Klimatet var mere arktiskt, har været 

 udbredt over hele vort Land, ogsaa i Lavlandet, 

 men derjma, etterhvert som Klimatet forandrede sig, 

 liar trukket sig tilbage nordpaa og tillige til Hoide- 

 ])lateauerne, hvor de klinu^tiske Forhold mere lig- 

 nede de oprindelige ; med andre Ord : den er her Syd 

 i Landet at l)etrag'te som en saakaldt «relict» Form, 

 en Levning fra den arktiske Fauna, der for i Tiden 

 var udbredt over vort liele Land. 



Da de Smaatjern og Damme, hvori den lever, 

 regelmæssigt udtørres mod Slutningen af Sommeren, 

 og væsentlig kun skylder sin Tilbliven Snesmeltnin- 

 geu paa Forsommeren, er denne Forms Levetid kun 

 indskrænket til nogle faa Maaneder af Aaret. I 

 Lobet af forholdsvis kort Tid har den imidlertid 

 gjennemgaaet sin Udvikling, og deretter gaar For- 

 jilantningen liurtigt for sig. r)e i Ægsækken inde- 

 holdte ^lOg, Ijliver, som anfort, altid omgivne meden 

 meget tyk Skul og er aabenbart alle beregnede paa 

 at overvintre, for til don folgende Sommer at ud- 

 vikle sig til cu ny Cicneration. Arten er saaledes 

 for hvert Aar kun repi'ii'senteriit ved en enkelt (le- 

 neration. J-ilggeni' atsættes i Mudret p;uv Jiunden 

 af Dammen, og da denne Afsætniiig afÆg foregaar 

 gjentagne (iange af hvxMt 1 1 iiiiiiidixid, vil dn- snart 

 o])h(jbe sig en anseelig Mu'ugde afÆg, der vil sikre; 

 Artens TilvH>relse ])aa de Steder, der er gunstige 

 for deus Ti'i\sel. Det er forst ved Midsoiunu'rtid, 



Avith no In'istles Avhatever. If the young one is 

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

 duction of these antennæ takes place, whereby they 

 assume the a])pearance, characteristic of the females, 

 of 2 simple triangular flajis. 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. 



Owureiice and Habits. 



The present Pli\-llo|)od seems to occur ver\- 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 Polyartrmia forcipata: in a similar 

 lake at Vardo, and in several small lakes and 

 shallow ponds on the mainland east of Vardo. It 

 has also been found by Prof. Lilljeborg at the North 

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

 not observed it, nor ,yet an3'where 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 

 dry u]) 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 lew months of the year. In 

 the course of a com])aratively short time, however, 

 it has passed through its developmental course, and 

 propagation then |U'occeds ra])idly. As already .stated, 

 the eggs in tlu' ovisac always become surrounded by 

 a very thick shell, and are cvidentl\- calculat(Hl to 

 stand the winter, and in the ensuiug summer to 

 develop iiit(] a new gencratidu. The species is thus 

 represented every year oidy 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 b\- each female, a consideralde 

 niimbcr of eggs is sr)ou amassed, which ensures the 

 existence (iC the sjiccies in those places that are favor- 

 able to its well-being. It is not until Midsumuu'r 



