114 



senere i den Anledning anstillede noiere Under- 

 soo-elser bar dog ikke forekommet mig overlaevi- 

 sende nok til at jeg tor fastliolde denne Oplatning. 



Hoist mærkværdig er Æggenes lange Leve- 

 dygtighed, der endog sjTies at hamle op med den 

 vel bekjendte seige Spireevne hos længe ophevarede 

 Plantefro. Som ovenfor anfort, forsynede jeg mig 

 Sommeren 188'.l med et storre Qvantum af toii-et 

 Miidder fra den Aaret iforveien af Prof. Collett 

 undersogte Knip ved Hamar. Af dette Mudder, som 

 jeg har staaende i en liden Kasse paa mit Laboratorium 

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

 liver Sommer iidtaget Sraaaportioner 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 Acjvarierne, og af disse Larver 

 har i Regelen ialfald en Del gjennemgaaet sin hele 

 Udvikling. De paa denne Maade kunstigt opdræt- 

 tede Lidivider 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 Maximums.storrelse 

 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 Ijimnadier, der lader sig 

 udklække af Mudret. Ganske nylig har jeg i et 

 opvarmet Enm gjort et nyt Forsog med det samme 

 Mudder, og ogsaa denne Gang, altsaa fulde 6 Aar 

 etterat Mudret l)lev 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 Literesse at faa paa denne Maade 

 sikkei't eonstateret Udstrækningen af Æggenes Le ve- 

 dj-gtighed. 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, skjoiult 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 heretter 

 næsten som om Æggene af Liranadia trænger, for 

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

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

 trnrfet denne Phyllopode i 2 paafolgende Aar paa 

 de samme Lokaliteter, kan ikke egentlig siges at 

 modl)evise en saadan Hyjiotliese, da det ']i) aldeles 

 ikke er afgjort, at de paatrufne individer netop 

 er udklækkede af de den foregaaende Sommer af- 

 satte Æg. 



De eiendiimnielige vingeforniige Udvidningcr, 



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 A'itality 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 ])rovided myself, in the 

 summer of 1889, with a considerable quantity of dried 

 mud from tlie pool near Hamar, examined by Prof. 

 ('oUett the year before. Of this mud, which stands 

 in a little box in mj- 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 experiments 

 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 lived 

 in my aquaria more or less far on towards the end 

 of the .summer. They have ajiparently thriven \\p1]. 

 have produced their egg-masses, and have generally 

 attained the same maximum size as the natui'ally- 

 reared specimens collected by me. At the first 

 attempts, vai-ions 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 hatclied in considerable 

 numbers, in spite of the disadvantageous time of 

 year (it is the I8th Feliruary 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 jirove.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, although the residuum lias 

 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 aljle to 

 develope, require to lie dry, not one year only, but 

 several years in succession. The fact that on Mærdø 

 1 have met witli this Phyllopod in the same loca- 

 lities 2 years in succession, cannot really be said 

 to disprove such a hyi>othesis, as it is not at all cer- 

 tain that the specimens found were hatched from 

 eggs deposited the previous summer. 



The ju'culiar wing-like expansions with which the 



