110 



skiftningen er Valvlerne forsynede med nok en 

 Væxtstribe udenom den Iste, en ny Ægraasse dan- 

 nes og saaledes fremdeles. Antallet af paa hinan- 

 den folgende Hudskiftninger er derfor, iberegnet den, 

 der er gaaet umiddell)art forud for Iste postlarvale 

 Stadium, noiagtig det samme som Antallet af Væxt- 

 striber i)aa hver Valvel, og omtrent ligemange 

 Gange Lar i Regelen Individet afsat en Ægmasse. 

 Efterlivert som Skallen paa denne Maade ved ny- 

 dannede peripliere Lag tiltager i Storrelse, foran- 

 dres lidt efter lidt dens Form, idet llygkanten bli- 

 ver mere og mere buet i sin forreste Del. Samtidigt 

 bliver de primære Valvler ligesom skudt fortil og 

 indtager tilsidst en forholdsvis liden Del af Skallen 

 ved dennes overste forre.ste Hjorne, hvilket sidste i 

 samme Forhold bliver utj'deligere og mere afstumpet 

 (se Fig. 1). Hos meget gamle Individer antager 

 Skallen til.sidst, seet fra Siden, en næsten triangulær 

 Form, med den primære Area skudt helt fortil og 

 næsten umboformigt fremragende, saaledes som an- 

 tj'det paa den af Prof. Lilljeborg givne Figur 

 (Skallen i naturlig Storrelse). 



Forekomst oa: Leveyis. 



Allerede Grulie har opgivet, at der i Berliner- 

 Museet tindes opbevaret Exemplarer af denne Form, 

 indsamlede af H. Rathke i Norge. Men da dette 

 Fund ikke med et eneste Ord er omtalt i den sidst- 

 nævnte Forskers bekjendte Værk: «Beitrage zur 

 Fauna Norwegens», og jeg selv under mine mange- 

 aarige Undersogelser af vor Ferskvandsfauna aldrig 

 havde ]iaatrutfet den, fandt jeg Paalideligheden af 

 denne Opgift af Clrube meget tvivlsom og iidtalte 

 mig ogsaa derhen i en i Vid. Selsk. Forhandlinger 

 meddelt forelobig Meddelelse om Norges Phyllopoder. 

 Forst i Aaret 1.S85 lykkedes det mig med fuld Sik- 

 kerhed at faa constateret denne eiendommelige Phyl- 

 lopodes Forekomst her i Landet. Under en Reise, 

 jeg dette Aar foretog langs Sydkysten af Landet, 

 tog jeg d. 22de Juli Station paa en ikke meget stor 

 og temmelig flad 0, '<Mærdo», udenfor Arendal, og 

 fandt her allerede den forste Dag efter min Ankomst 

 store Mængder af Limnadia-Larver i et grundt med 

 (xræsbund forsynet Tjern, «Storekjær^ kaklet, be- 

 liggende omtrent midt paa Øen. Paa denne Tid var 

 kun meget faa Exemplarer naaet ud over Lai've- 

 tilstanden, men i Lol)et af de folgende Dage op- 

 traadte postlarvale Stadier i stor Mængde, og ved 

 Slutten af Maaneden var ingen Larve længere at 

 tinde. Flere Exemplarer var da allerede ægbæ- 

 rende og havde Valvlerne forsynede med de forste 

 Væxtstriber. Ved min Afreise, d. 10de August, var 

 Skallen hos de storste Individer omtrent 10 mm. 

 lang og havde 5 Par Væxtstriber. Foi' om muligt 

 at tinde fuldvoxne Individer, besogte jeg igjen Oen 



skin, out of the shell behind. After the exuviation 

 the valves acquii-e another line of growth outside 

 tlie hrst, a new mass of eggs is formed, and so on. 

 Tlie numV)er of successive exuviations, including 

 that which immediately ])reeeded the 1st post-larval 

 stage, is therefore exactly the same as the number 

 of lines of growth on each valve, and the animal 

 has, as a rule, de])osited a mass of eggs about the 

 same numljer of times, ^^^lile the shell in this 

 manner increases in size by tlie addition of new 

 peripheral layers, it gradually changes its shape, 

 the dorsal edge becoming more and more curved in 

 its front part. At the same time the original valves 

 are as it were pressed foi'ward, and at last occupy 

 a comparatively small part of the shell at its upper 

 front angle, which also, in tlie same proportion, be- 

 comes more indistinct and bhmter (see fig. 1). In 

 very old specimens the shell, seen from the side, at 

 last assumes an almost triangular shape, with the 

 original area jnished right to the front, and jn-o- 

 jecting almost umbonately, as indicated in tlie 

 figure given Ijy Prof. Lilljeborg (the shell in its 

 natural size). 



Occurrence and Habits. 



Grube has already stated that in the Berlin 

 Museum there are preserved sjjecimens of this form, 

 collected by A. Kathke in Norway. But as this 

 discovery is not so much as named in the latter 

 naturalist's well-kno\\'n work «Beitrage zur FaTina 

 Norwegens», and I myself, diiring my many years' 

 investigations of our (Norwegian) fresh-water fauna, 

 had never met with the form, I considered the 

 trustworthiness of Grube's statement to be very 

 doixbtful, and expressed myself to that etfect in a 

 preliminary account of the Pliyllopoda of Norway 

 in the Viden. Selsk. Forhandlinger (Proceedings of 

 the Scientific Society). Not until the year 1885 did 

 I succeed in substantiating with certainty the 

 occurrence of this peculiar Phyllopod in this country 

 (Norway). During a jovrrney I made that year 

 along the south coast, I sto])ped, on the 22nd July, 

 at a rather fiat, and not very large island otf Aren- 

 dal, called <Mæi'doi, and tliere found, on the very 

 day after my arrival, large numbers of Limnadia 

 larvæ in a shallow lake called «Storekjær», situated 

 in about the middle of the island, and mth a grassy 

 bottom. At that time only a very few specimens 

 were advanced beyond the larval condition, but in 

 the course of the few following days, post-larval 

 stages made tlieir apjiearance in great numl)ers, and 

 ])y the end of the montli there was not a larva to 

 be found. Several specinu'us were then already 

 carrying eggs, and had their valves furnished with 

 the first lines of growth. At tiie time of my 

 deiiarture. the 10th Auo'ust, tlie shells on tlie 



