82 



1 senere Stadier reduceres 2det Par Folere mere 

 og mere og taber tilsidst sine Svommebor.ster fuld- 

 stændigt, hvorved deres Betydning som Bevæge- 

 organer er opliort. Bevægelsen overtages nu ude- 

 Inkkende af de mere fuldkomraent udviklede Fodder. 

 Halepladen begynder saa smaat at forlænge sig og 

 faar flere Eandtorne, men er endnn Los temmelig 

 store Unger meget liden (se Tab. XIII, Fig. 2S). 



Levevis. — Xæi'værende Phyllopode synes ikke, 

 som Tilfældet er med de fleste ovrige Former, at 

 være udeliikkende indskrænket til mindre A-'and- 

 ansamlinger, som ud paa Summeren torrer ganske 

 eller delvis nd. Jeg bar tvertiniod hidtil kun fun- 

 det den i temmelig store og dybe Vande, og bar 

 seet den paa D\d)der af mindst o — 4 Favne. Som 

 Regel holder den sig lige ved Bunden og svømmer 

 langs denne, altid med Byggen opad. Men ikke saa 

 sjelden tager den sig ogsaa Udflugter hoiere op i 

 Våndet og vender herunder snart Byg, snart Bug 

 opad, eller dreier sig rundt paa forskjellig Vis. 

 Svømningen tilveiebringes hos det voxne I)\'r ude- 

 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 tyder 

 paa, at Dyret hovedsageligt lever af Rov, rimeligvis 

 for en stor Del af andre Entomostraceer. Jeg har 

 ogsaa ikke sjeldent mellem Fodderne i)aa dem fun- 

 det Dajdinier og forskjellige ('ojiejtoder {Cydops. 

 Helerorope). Efter Sigende skal den i visse Tilfælde 

 ogsaa fortære Fiskerogn og derved blive skadelig 

 for Fiskebestanden i de Vande, hvori den fore- 

 kommer. 



De a.llerfleste Individer, man træffer, er afHun- 

 kjon, og det er forst efter et meget noie Ettersyn 

 af talrige Exemplarer, at det er lykkets mig at 

 linde frem nogle faa Hanner. Efter al Sandsynlig- 

 hed er Hannernes Forekomst kun indskrænket til 

 en ganske kort Periode, rimeligvis til Slutten af 

 Sommeren. 



Forekomst. — Selv har jeg her i Landet kun 

 trnifet den paa Filefj elds Hoideplatéau, omkring Ny- 

 stuen, dels i selve Nystuvandet eller i Udvidningen 

 af den fra samme mod Vest udgaaende Elv, dels i 

 et Fjeldvand, Vesleskartjernet kaklet, paa selve 

 Xystufj eldets Ryg og i en Hoide af cirea 4000 Fod 

 over Havet. I det sidstnæ^^lte Vand, der er tem- 

 melig dybt, fandtes den i Slutningen af Augu.st 1887 

 i stor Mængde, og kunde fra Stranden af gjennem 

 det krystalklare Vand sees overalt paa Bunden. 

 Kun undtagelsesvis fandtes den saa nær Stranden 

 og paa saa gruudt A^and, at den kunde tåges med 

 en almindelig Haand-Haav, og min Fangst af den 

 indskrænkede sig derfor ogsaa, forste Gang, jeg be- 

 sogte dette Vand, kun til nogle laa 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 production 

 of motion is now undertaken exclusiveh' by the 

 more fully developed legs. The caudal lamina com- 

 mences slightly to lengthen, and acquii'es several 

 marginal spines, bi\t is still, even in rather large 

 young ones, very small (see PI. XIII, fig. 28). 



Habits. — Tlie present Phyllopod does not seem, 

 as is the case with most of the other foi'ms, to be 

 exclusively confined to small pieces of water, wliich 

 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 deptlis 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 sui'face uppermost, or twists 

 about in various ways. The action of swimming 

 in the full-grown aninu^l 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 infre(|uently found 

 between its legs Daphniæ and various Copepods 

 {Cyclopg, Hefe)-oco2)e). According to report, it has 

 also, in certain cases, been knoAvn to consume fish- 

 spawn, and is thus detrimental to the stock of fish 

 in the lakes where it occurs. 



The greater nunfljer of specimens met with are 

 of tlie female sex, and it is only after a very care- 

 ful examination of numercnis specimens that I have 

 succeeded in finding a few males. In all probability, 

 the occi^rrence of the males is limited to (juite a 

 short period, probably until the end of the summer. 



Occurrence. — In this country (X^orway) I have 

 ])ersonal]y only met with this form on tlie high 

 plateau of the Filefj eld, aboiit 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 Veslcskartjern, on the ridge 

 of Nystue Moxintain, and at a height of about 40Q0 

 feet above the sea. In the last-named lake which 

 is rather deeji, this species was found at the end of 

 August, 1887, in great numbers, and could be seen 

 from the sliore, through tlie clear water, all over 

 the liottoin. -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 

 tliat mv take of it, the first time I visited tliis lake, 



