82 



1 senere Stadier reduceres 2det Par Folere mere 

 og mere og taber tilsidst sine Svømmebørster fuld- 

 stændigt, hvorved deres Betydning som Bevæge- 

 organer er opliort. Bevægelsen overtages nu nde- 

 lukkende af de mere fnldkomment udviklede Fødder. 

 Halepladen begynder saa smaat at forlænge sig og 

 faar flere Eandtorne, men er endnu lios temmelig 

 store Unger meget liden (se Tab. XIII, Fig. 28). 



Levevis. — Nærværende Phyllopode synes ikke, 

 som Tilfældet er med de fleste ovrige Former, at 

 være udelukkende indskrænket 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 svømmer 

 langs denne, altid med Ryggen opad. Men ikke saa 

 sjelden tager den sig ogsaa Udflugter hoiere op i 

 Våndet og vender herunder snart Ryg, snart Bug 

 opad, eller dreier sig rundt paa forskjellig Vis. 

 Svømningen tilveiebringes hos det voxne Dyr nåe- 

 lukkende ved Hjælp af Fodderne og foregaar med 

 en ganske jevn og ikke meget hurtig Fart. 



De grovt tandede Kindbakker og de stærke klo- 

 formige Enditer paa de forreste Par Fodder tjder 

 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 {Cjidops. 

 Heterocopé). Efter Sigende skal den i visse Tilfælde 

 ogsaa fortære Fiskerogn og derved blive skadelig 

 for Fiskebestanden i de Vande, livori den fore- 

 kommer. 



De allerfleste Individer, man træffer, er afHiin- 

 kjøn, og det er forst efter et meget nøie Ettersyn 

 af talrige Exemjilarer, at det er lykkets mig at 

 finde frem nogle faa Kanner. Efter al Sandsynlig- 

 hed er Haunernes Forekomst kun indskrænket til 

 en ganske kort Periode, rimeligvis til Slutten af 

 Sommeren. 



Forekomst. — Selv har jeg her i Landet kim 

 trufFet den paa Filefj elds Hoideplateau, omkring Ny- 

 stuen, dels i selve Nystuvandet eller i Udvidningeu 

 af den fra samme mod Vest iidgaaende Elv, dels i 

 et Fjeldvand, Vesleskartjernet kaldet, paa selve 

 Nystufj eldets Ryg og i en Hoide af circa 4O0O Fod 

 over Havet. I det sidstnævnte Vand, der er tem- 

 melig dybt, fandtes den i Slutningen af August 1887 

 i stor Mængde, og kunde fra Stranden af gjennem 

 det krj^stalklare Vand sees overalt paa Bunden. 

 Kun undtagelsesvis fandtes den saa nær Stranden 

 og paa saa grundt Vand, at den kvinde tåges med 

 en almindelig Haand-Haav, og min Fangst af den 

 indskrænkede sig derfor ogsaa, første Gang, jeg be- 

 søgte dette Vand, kun til nogle faa Exemplarer. 



In later stages the 2nd pair of antennæ 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 prodiiction 

 of motion is now iindertaken 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 PI. 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, whick 

 either quite or partialh^ dry up towards the end 

 of the summer. On the contrar}', I have liitherto 

 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 prejdng 

 on others, probably to a large extent on other En- 

 tomostraca. I have also not infrequently found 

 between its legs Daphniæ 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 

 personalh' onlj^ met with this form on the high 

 plateau of the Filefjeld, about Nystuen, partly in 

 Nj'stue 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, 



