114 



senere i den Anledning anstillede noiere Under- 

 søgelser har dog ikke forekommet mig overbevi- 

 sende nok til at jeg tor fastholde denne Opfatning. 



Hoist mærkværdig er Æggenes lange Leve- 

 dvgtighed, der endog s;y-nes at hamle op med den 

 vel bekjendte seige Spireevne hos længe opbevarede 

 Plantefrø. Som ovenfor anfort, forsj-nede jeg mig 

 Sommeren 1889 med et større Qvantum af tørret 

 JIndder fra den Aar et ifoi-veien af Prof. Collett 

 undersogte Kiiljj ved Hamar. Af dette Mixdder, som 

 jeg har staaende i en liden Kasse paa mit Laboratorium 

 i den Tilstand, hvori det blev tåget, har jeg senere 

 hver Sommer udtaget Smaaportioner og dermed an- 

 stillet Udklækningsforsøg i mine Aqvarier. Disse Ud- 

 klækning-sforsøg har endnn ikke nogen Gang slaaet 

 feil. Altid har store Mængder af Larver inden meget 

 kort Tid vist sig i Aqvarierne, og af disse Larver 

 har i Regelen ialfald en Del gjennemgaaet sin hele 

 Udvikling. De paa denne Maade kunstigt opdræt- 

 tede Individer har jeg havt gaaende i mine Aqva- 

 rier mere eller mindre langt nd over Sommeren. De 

 har tilsyneladende trivets udmærket, har paa sæd- 

 vanlig Vis prodnceret sine Ægpaketter og har ial- 

 mindelighed naaet den samme Maximumsstørrelse 

 som de af mig frit indsamlede Exemplarer. Ved de 

 første Forsog udklækkedes sammen med Limnadierne 

 ogsaa forskjellige andre Entomostraceer ; men i de 

 senere Aar er det alene Limnadier, der lader .sig 

 iidklække af Mudret. Ganske nylig har jeg i et 

 opvarmet lium gjort et nyt Forsog med det samme 

 Mudder, og ogsaa denne Gang, altsaa fulde 6 Aar 

 efterat Mudret blev tåget, ser jeg, at Larver ud- 

 klækkes i temmelig betydeligt Antal, trods den 

 uheldige Aarstid (vi skriver idag, da dette ned- 

 skrives, den 18de Februar). Det er min Agt at 

 fortsætte Experimenterne fremdeles med den tilovers- 

 blevne Rest af Muddret, da det forekommer mig at 

 have adskillig Interesse at faa paa denne Maade 

 sikkert constateret Udstrækningen af Æggenes Le ve- 

 dygtighed. En ganske besynderlig Omstændighed 

 maa jeg her nævne, og det er, at det endnu ikke 

 har lykkets mig at faa de i mine Aqvarier afsatte 

 Æg af denne Form udklækkede, .skjondt Residuet 

 er behandlet paa samme Maade som ved andre Ud- 

 klækningsforsøg, idet jeg liar ladet det ligge i ind- 

 torret Tilstand Vinteren over. Det sj'nes herefter 

 næsten som om Æggene af Limnadia trænger, for 

 at kvinne udvikle sig, at ligge torre ikke blot et, 

 men flere Aar itræk. At jeg paa Mærdø har paa- 

 truflFet denne Phyllopode i 2 paafolgende Aar paa 

 de samme Lokaliteter, kan ikke egentlig siges at 

 modbevise en saadan Hypothese, da det jo aldeles 

 ikke er afgjort, at de paatrufne Individer netop 

 er udklækkede af de den foregaaende Sommer af- 

 .satte Æg. 



De eiendommelige vingeformige Udvidninger, 



but the results of more careful observations made 

 by me subsequently, have not appeared to me to 

 be sufficiently convincing to permit of my main- 

 taining that view. 



The great vitality of the eggs is most remar- 

 kable, and seems to be on a par with the well-known 

 tenacious germinating power in long preserved plant 

 seeds. As already stated, I provided myself, in the 

 summer of 1889, with a considerable quantity of dried 

 mud from the pool near Hamar, examined by Prof. 

 Collett the year before. Of this mud, which stands 

 in a little box in my laboratory, in the condition 

 in which it Avas taken, I have since then, every sum- 

 mer, taken out small quantities, and made hatching- 

 experiments in my aqiiaria. These exjjeriments 

 have never yet been unsuccessful. Always, within a 

 very short period of time, large numbers of larvæ 

 have made their appearance in the aquaria, and, as ' 

 a rule, a proportion, at any rate, of these larvæ 

 have gone through their whole development. The 

 specimens artificially reared in this way have li-^'ed 

 in my aquaria more or less far on towards the end 

 of the summer. They have apparently thriven well, 

 have produced their egg-masses, and have generally 

 attained the same maximum size as the naturall}'- 

 reared specimens collected by me. At the first 

 attempts, vai'ious other Entomostraca were hatched 

 with the Limnadiæ; but in the later j^ears, 

 Limnadiæ only have been hatched from the mud. 

 I have quite recently made a fresh trial with the 

 same m\id in a heated room; and this time too, 

 fully six years after the mud was taken, I see 

 that the larvæ are being hatched in considerable 

 numbers, in spite of the disadvantageoits time of 

 year (it is the I8th February when I write this). 

 It is my intention to continue the experiments with 

 the remainder of the mud, as it appears of conside- 

 rable interest to me to prove with certainty in this 

 way the extent of the period of the eggs" vitality. 

 One very peculiar circumstance I must mention 

 here, namely, that I have not yet succeeded in 

 hatching out any of the eggs deposited in my 

 aquaria by this form, althoiigh the residuum has 

 been treated in exactly the same way as in other 

 hatching experiments, as I have left it in a dried-up 

 condition throughout the winter. It seems from this 

 as if the eggs of Limnadia, in order to be able to 

 develope, require to lie dry, not one j-ear only, but 

 several years in succession. The fact that on Mærdo 

 I have met with this Phyllopod in the same loca- 

 lities 2 yearg in succession, cannot really be said 

 to disprove such a hj'pothesis, as it is not at all cer- 

 tain that the specimens found were hatched from 

 eggs deposited the previous summer. 



The peculiar wing-like expansions with which the 



