114 



senere i den Anledning' an.stillede noiere Under- 

 søgelsei' har dog ikke forekommet mig overbevi- 

 sende nok til at jeg tor fastholde denne Opfatning. 



Hoist mærkværdig er Æggenes lange Leve- 

 dvgtighed, der endog synes at hamle op med den 

 vel bek j endte seige Spireevne hos længe opbevarede 

 Plantefro. Som ovenfor anfort, forsj-nede jeg mig 

 Sommeren 188'J med et storre Qvantum af torret 

 Mndder fra den Aaret iforveien af Prof. Collett 

 nndersogte Knip ved Hamar. Af dette Mudder, som 

 jeg har staaende i en liden Kasse paa mit Laboratorium 

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

 hver Sommer udtaget Smaaportioner og dermed an- 

 .stillet Udklækningsforsog i mine Aqvarier. Disse Ud- 

 klækningsforsog har endnu 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 

 Ud vikling. De paa denne Maade ki^nstigt opdræt- 

 tede Individer har jeg havt gaaende i mine Aqva- 

 rier mere eller mindre langt ud over Sommeren. De 

 har tilsyneladende trivets udmærket, har paa sæd- 

 vanlig Vis produceret sine Ægpaketter og har ial- 

 mindelighed naaet den samme Maximumsstørrelse 

 som de af mig frit indsamlede Exemjjlarer. Ved de 

 forste Forsog udklækkedes sammen med Limnadierne 

 ogsaa forskjellige andre Entomostraceer ; men i de 

 senere Aar er det alene Limnadier, der lader sig 

 udklække af Mudret. Ganske nylig har jeg i et 

 opvarmet Rum gjort et nyt Forsøg med det samme 

 Mudder, og ogsaa denne Gang, altsaa fulde 6 Aar 

 etterat Mudret blev tåget, ser jeg, at Larver iid- 

 klækkes i temmelig betvdeligt 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 Leve- 

 dygtighed En ganske be.synderlig Om.stændighed 

 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, skjøndt Residuet 

 er behandlet paa samme Maade som ved andre Ud- 

 klækningsforsog, idet jeg har ladet det ligge i ind- 

 torret Tilstand Vinteren over. Det synes herefter 

 næsten som om Æggene af Limnadia trængei-, for 

 at kunne iidvikle sig, at ligge torre ikke blot et, 

 men tiere Aar itræk. At jeg paa Mærdo har paa- 

 truftet 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 peimit of my main- 

 taining that view. 



The great vitality of the eggs is most remar- 

 kable, and seems to be on a par wåth the well-knovs^n 

 tenacious gei'minating 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 was taken, I have since then, every sum- 

 mer, taken out small quantities, and made hatching- 

 experiments in my aquaria. These exjieriments 

 have never yet been un.successful. 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 artifirially reared in this way have lived 

 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 naturally- 

 reared specimens collected by me. At the first 

 attempts, various other Entomostraca were hatched 

 with the Limnadiæ; but in the later years, 

 Limnadiæ only have been hatched from the mud. 

 I have quite recently made a fresh trial with the 

 same mud 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 disadvantageoiis 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 mu.st mention 

 here, namely, that I have not yet succeeded in 

 liatching out any of the eggs deposited in my 

 aqi^aria by this foi'm, although 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 year only, Init 

 several years in succession. The fact that on Mærdo 

 I have met with this Phyllopod in the same loca- 

 lities 2 years in succession, cannot really be said 

 to disprove such a hypothesis, 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 whicli the 



