__ 82 
I senere Stadier reduceres 2det Par Folere mere 
og mere og taber tilsidst sine Svommeborster fuld- 
steendigt, hvorved deres Betydning som Bevege- 
organer er ophort. Bevegelsen overtages nu ude- 
lukkende af de mere fuldkomment udviklede Fodder. 
Halepladen begynder saa smaat at forleenge sig og 
faar flere Randtorne, men er endnu hos temmelig 
store Unger meget liden (se Tab. XIII, Fig. 28). 
Levevis. — Nerverende Phyllopode synes ikke, 
som Tilfeeldet er med de fleste ovrige Former, at 
vere udelukkende indskrenket til mindre Vand- 
ansamlinger, som ud paa Sommeren torrer ganske 
eller delvis ud. Jeg har tvertimod hidtil kun fun- - 
det den i temmelig store og dybe Vande, og har 
seet den paa Dybder af mindst 3—4 Favne. Som 
Regel holder den sig lige ved Bunden og svommer 
langs denne, altid med Ryggen opad. Men ikke saa 
sjelden tager den sig ogsaa Udflugter hoiere op i 
Vandet og vender herunder snart Ryg, snart Bug 
opad, eller dreier sig rundt paa forskjellig Vis. 
Svomningen tilveiebringes hos det voxne Dyr ude- 
lukkende ved Hjelp af Fodderne og foregaar med 
en ganske jevn og ikke meget hurtig Fart. 
De grovt tandede Kindbakker og de sterke klo- 
formige Enditer paa de forreste Par Fodder tyder 
paa, at Dyret hovedsageligt lever af Rov, rimeligvis 
for en stor Del af andre Entomostraceer. Jeg har 
ogsaa ikke sjeldent mellem Fodderne paa dem fun- 
det Daphnier og forskjellige Copepoder (Cyclops, 
Heterocope). Efter Sigende skal den i visse Tilfelde 
ogsaa fortere Fiskerogn og derved blive skadelig 
for Fiskebestanden i de Vande, hvori den fore- 
kommer. 
De allerfleste Individer, man treffer, er af Hun- 
kjon, og det er forst efter et meget noie Eftersyn 
af talrige Exemplarer, at det er lykkets mig at 
finde frem nogle faa Hanner. Efter al Sandsynlig- 
hed er Hannernes Forekomst kun indskrenket. til 
en ganske kort Periode, rimeligvis til Slutten af 
Sommeren. 
Forekomst. — Selv har jeg her i Landet kun 
truffet den paa Filefjelds Hoideplateau, omkring Ny- 
stuen, dels i selve Nystuvandet eller i Udvidningen 
af den fra samme mod Vest udgaaende Ely, dels i 
et Fjeldvand, Vesleskartjernet kaldet, paa selve 
Nystufjeldets Ryg og i en Hoide af circa 4000 Fod 
over Havet. I det sidstnevnte Vand, der er tem- 
melig dybt, fandtes den i Slutningen af August 1887 
i stor Mengde, og kunde fra Stranden af gjennem 
det krystalklare Vand sees overalt paa Bunden, 
Kun undtagelsesvis fandtes den saa ner Stranden 
og paa saa grundt Vand, at den kunde tages med 
en almindelig Haand-Haav, og min Fangst af den 
indskrenkede sig derfor ogsaa, forste Gang, jeg be- 
sogte dette Vand, kun til nogle faa Exemplarer. 
In later stages the 2nd pair of antennee become 
more and more reduced in size, and at last entirely 
lose their natatory bristles, whereby their impor- , 
tance as organs of motion ceases. The production 
of motion is now undertaken exclusively by the 
more fully developed legs. The caudal lamina com- 
mences slightly. to lengthen, and acquires several 
marginal spines, but is still, even’ in rather large 
young ones, very small (see Pl. XIII, fig. 28). 
Habits. — The present Phyllopod does not seem, 
as is the case with most of the other forms, to be 
exclusively confined to small pieces of water, which 
either quite or partially dry up towards the end 
of the summer. On the contrary, I have hitherto 
only found it in rather large and deep lakes, and 
have seen it at depths of at least 3 or 4 fathoms. 
As a rule, it keeps to the bottom, where it swims 
along, always with its back uppermost; but it not 
infrequently makes excursions higher up in the 
water, and during these, turns sometimes its back, 
sometimes its ventral surface uppermost, or twists 
about in various ways. The action of swimming 
in the full-grown animal is performed exclusively 
by the aid of the legs, and at a perfectly even, 
and not very rapid rate. 
The coarsely dentated mandibles, and the strong, 
claw-like endites of the foremost pairs of legs indi- 
cate that this animal lives principally by preying 
on others, probably to a large extent on other En- 
tomostraca, I have also not infrequently found 
between its legs Daphnie and various Copepods 
(Cyclops, Heterocope). According to report, it has 
also, in certain cases, been known to consume fish- 
spawn, and is thus detrimental to the stock of fish 
in the lakes where it occurs. - 
The greater number of specimens met with are 
of the female sex, and it is only after a very care- 
ful examination of numerous specimens that I have 
succeeded in finding a few males. In all probability, 
the occurrence of the males is limited to quite a 
short period, probably until the end of the summer. 
Occurrence. — In this country (Norway) I have 
personally only met with this form on the high 
plateau of the Filefjeld, about Nystuen, partly in 
Nystue Lake itself and the expansions of the river 
flowing out of it towards the west, and partly in a 
mountain tarn called Vesleskartjern, on the ridge 
of Nystue Mountain, and at a height of about 4000 
feet above the sea, In the last-named lake which 
is rather deep, this species was found at the end of 
August, 1887, in great numbers, and could be seen 
from the shore, through the clear water, all over 
the bottom. Only in exceptional cases was it found 
so near the shore and in such shallow water, that 
it could be taken with an ordinary hand-net, so 
that my take of it, the first time I visited this lake, 
