a 
ee 
eller i Juli Maaned, at man hos os ialmindelighed | 
finder denne Form fuldt udviklet. Jeg har paa 
denne Tid observeret den i store Mengder i Smaa- 
tjern paa Dovres Hoideplateau, Ost af Jerkin. Som 
-Tilfeeldet synes at vere med de fleste Phyllopoder, 
naar den temmelig tidligt, og lenge for den er fuldt 
udvoxet, Kjonsmodenhed. De storste Individer fin- 
der man derfor ialmindelighed lengere ud paa Ho- 
sten, medens Storrelsen forst paa Sommeren er be- 
tydelig ringere. Ofte er der ogsaa paa samme Tid 
adskillig Forskjel i Storrelsen i forskjellige ner 
liggende Tjern. I samme Tjern finder man derimod 
i Regelen alle Individer omtrent ens udviklede og 
af ens Farve. 
Det er et meget livligt Dyr, som er i uafbrudt 
Beveegelse, oftest mere eller mindre ner Overfladen 
af Vandet. Bevegelsen tilveiebringes hovedsageligt 
ved Branchialfoddernes Svingninger, der foregaar 
paa en meget regelmessig og elegant Maade, idet 
de ikke sker noiagtig samtidigt for alle Fodders 
Vedkommende men successivt, hvad der giver Ind- 
trykket af en eindommelig Undulation i Bevegelsen. 
Den herved frembragte Lokomotion er en ganske 
jevn i horizontal Retning, hvorunder Dyret altid 
vender Ryggen nedad. Dog kan det foretage mange 
' forskjellige Volter i Vandet og dreie og sno sig i 
alle Retninger, hvorved Halens Bevegelser spiller 
en veesentlig Rolle. Hanner og Hunner sees ofte j 
Kopulation, idet Hannen med sine Gribeantenner 
fast omslutter Hunnens Genitalsegment fra Ryggen 
af, og saaledes kan begge Individer svomme om i 
lange Tider, begge vendende Bugsiden opad. Selve 
Kopulationsakten har jeg ikke faaet observeret. 
Rimeligvis afventer Hannen det Qieblik, da de 
modne AXg fra Ovarierne treder ind fi Basis af 
Rugesekken, hvor de, som ovenfor anfort, omgives 
af sin Skal. 
Dyrets Fode synes hovedsageligt at bestaa af 
mikroskopiske Alger og andre Plantedele, tildels vel 
ogsaa af Infusorier, der ved Branchialfoddernes Spil 
hvirvles ind mod Munden. 
Udbredning. — Nerverende Phyllopode er forst 
beskrevet fra Gronland, hvor den synes at vere 
meget almindelig, og er senere bleven gjenfunden 
paa flere andre Steder, saaledes det arktiske Ame- 
rika, paa Spitsbergen, Novaja Semlja, Kolahalvoen 
ogiSibirien. Idethele falder dens Udbredning, naar 
undtages det ovennevnte Findested i Norge paa 
Dovres Hoideplateau, udelukkende indenfor den ark- 
tiske Zone, og dens Forekomst her synes at stemple 
den som en egte arktisk og circumpolar Form. 
or July that this form is generally found fully 
developed here. At that season I have observed 
it in great numbers in small lakes on the high 
plateau of the Dovre Mountains, east of Jerkin. 
As seems to be the case with most Phyllopoda, it 
attains sexual maturity tolerably early, and long 
before it is fully grown. The largest specimens are 
therefore generally found later in the autumn, while 
the size in the beginning of the summer is very 
much smaller. There is also often considerable 
difference in their size in different lakes, while on 
the other hand, all the animals in one lake are, as 
a rule, uniformly developed, and uniform in colour. 
It is a very lively animal, and in constant 
motion, generally more or less near the surface of 
the water. The movement is chiefly brought about 
by the vibrations of the branchial legs, which take 
place in a very regular and graceful manner, not 
quite simultaneously with all the legs, but succes- 
sively, thereby imparting to the movement a peculi- 
arly undulatory effect. The motion thus produced 
is equable and in a horizontal direction, the back 
of the animal being always turned downwards. It 
may, however, make all kinds of springs in the 
water, turning and twisting in every direction, the 
movements of the tail playing an important part in 
these evolutions. Males and females are often seen 
in copulation, the male, with his prehensile antenne, 
firmly embracing the female’s genital segment from 
the back, and in this manner both animals may 
swim about for a long time with the ventral side 
uppermost. The act of copulation itself, I have not 
witnessed. The male probably awaits the moment 
when the mature ova enter from the ovary into the 
base of the marsupium, where, as previously stated, 
they are enveloped in their shell. 
The food of this animal seems to consist prin- 
cipally of microscopic alge and portions of other 
plants, partly also of infusoria, which are swept in 
towards the mouth by the movement of the bran- 
chial legs. 
Distribution. — The present Phyllopod was first 
described from Greenland, where it seems to be 
very common, and has since been found in several 
other places, e. g. arctic America, Spitzbergen, 
‘Novaia Zemlia, the Kola Peninsula and in Siberia. 
Altogether its distribution, with the exception of 
the above-named place in Norway, on the high pla- 
teau of the Dovre Mountains, is exclusively within 
the aretic zone, and its occurrence .there seems to 
stamp it as a true arctic and circumpolar form. 
8 —G. 0. Sars: Fauna Norvegix. 
