112 



sætte sine Æg, hvad der sikrer Artens fortsatte 

 Existens, om Forholdene et andet Aar skulde vise 

 sig gunstige for en ny Generations Udvikling. Som 

 Kegel synes det dog at være et meget lidet Procent- 

 tal af de utallige Larver, som i Begyndelsen ud- 

 klækkes, der virkelig kommer til fuld Udvikling. 

 Larver og Unger finder man uden Forskjel overalt 

 i de Vandansanalinger, hvori de træftes, lige saa 

 hyppigt tæt inde ved Bredden som nde paa dybere 

 Vand. Anderledes er det med fuldvoxne Exempla- 

 rer. Disse holder i Regelen kun til paa de dybeste 

 Steder af Dammen og her gjerne nær Bunden. Da 

 Dyrene i Eegelen er meget gjennemsigtige, er det 

 ikke saa godt at faa Øie paa dem fra Stranden af- 

 Dog vil ialmindelighed den opake gulbrune Æg- 

 masse forraade dem, navnlig naar Bunden, henover 

 hvilken de bevæger sig, bestaar af raorkt Mudder. 

 Bevægelsen er ikke synderlig hiirtig og har Clia- 

 racteren af et forholdsvis sagte og noget ujevnt 

 Lob, hvorunder i Regelen Ryggen vender opad. 

 Holdte i A(juarier kan man noiere studere deres 

 Bevægelser og ovrige Levevis. Der kan ikke være 

 nogen Tvivl om, at Dyrets hovedsageligste Be- 

 vægelsesorganer er Aarerne. Det er ved hurtigt 

 gjentagne Slag til Siderne af disse Lemmers ydre 

 Pai'ti, at Legemet l^liver drevet igjennem Våndet, 

 skjondt ogsaa Branchialfoddernes Svingninger tor 

 til en vis (xrad understøtte Bevægelsen. Stoder 

 Dyret under sine Bevægelser paa tætte Conferve- 

 masser, formaar det med stor Behændighed at ar- 

 beide sig igjennem dem, hvorved den meget bevæge- 

 lige Bagkrop spiller en vigtig Rolle. Idethele sees 

 Dyret meget ofte at foretage energiske Beininger 

 og Strækninger af denne Del af Legemet, dels for 

 at overvinde Hindringer for dets Passage gjennem 

 Våndet, dels for at befri det indre af Skallen for 

 fremmede indkomne Partikler. Meget ofte faar man 

 se, at Dyret med Forenden hefter sig fast til de i 

 Våndet værende Gjenstande, navnlig til Undersiden 

 af Blade eller Gonferver i Overfladen af Aqvarierne, 

 og forbliver i denne Stilling sædvanligvis i længere 

 Tid. Fastheftningen synes hovedsageligst at tilveie- 

 bringes ved de stærke hageformige Pigge langs For- 

 siden af Aarernes Grene, tildels ogsaa ved det eien- 

 dommelige fra Hovedets Dorsalside udgaaende kolle- 

 formige Appendix, som man ved noiere Undersogelse 

 altid vil linde er i umiddelbar ('ontact med den 

 Gjenstand, hvortil Dyret er fastklamret. Dyret er 

 herunder ikke i absolut Ro, men der foregaar en 

 svag rhytmisk Svingning af li eie Legemet frem og 

 tilbage, aabenbart foraarsaget ved de heftigt bevæ- 

 gede Branehialfodder. Disse Svingninger sker paa 

 fuldkommen samme Maade som hos Branchipodiderne, 

 idet de ikke er simultane men successive, hvad der 

 giver Indtrykket af en eiendommelig grazios Undu- 

 lation i Bevægelsen. Idethele er det meget sjelden 

 at denne svingende Bevægelse af Branchialfodderne 



some, at any rate, of the animals attain to sexual 

 maturity, and are able to deposit their eggs, thereby 

 ensuring the continued existence of the species, 

 should conditions another year l)e favorable for the 

 development of a new generation. As a rale, it 

 appears to be a very small jjercentagc of tlie innu- 

 meralde larvæ at first hatclied, that really become 

 fulh' developed. Larvæ antl 3'oung ones are found 

 witho\rt distinction all over the pieces of water in 

 which they are met with, ([uite as frequently close 

 to the bank as out in deeper water. It is otherwise 

 with fullgrown animals. They generally keep to 

 the deeper parts of the pond and near the bottom. 

 As the animals are generally very transparent, it 

 is not very easy to see them from the shore. The 

 opaijue, 3'eilowish brown mass of eggs, however, will 

 generally betray them, especiallj' if the bottom, 

 over which they move, consists of dark mud. The 

 motion is not remarkably ([uick, Init has the cha- 

 racter of a i'omparativel,\' slow and somewhat 

 I xmeven dart, during which the back is generally 

 uppermost. '\\^hen kept in an aquarium, its move- 

 ments and other habits may be more carefully stu- 

 died. There can lie no doubt that the animal's 

 most imj^ortant organs of locomotion are the oars. 

 It is by quickly repeated side-strokes of the 

 distal part of these limbs that the l)ody is driven 

 through the water, although the swinging of the 

 branchial legs may also, to a certain extent, assist 

 the movement. Should the animal, as it moves, 

 come in contact with thick masses of confervæ, it 

 manages with great dexterity to work its way 

 through them, the very mobile hind part of the 

 body playing an important part in that proceeding. 

 The animal may often be observed to make ener- 

 getic bends and extensions of this part of the body, 

 partly to overcome obstacles to its passage through 

 the water, partly to rid the shell of foreign par- 

 ticles that have entered. The animal may very 

 often be seen to attach itself by its anterior end 

 to objects in the water, especially to the under 

 surface of leaves or confervæ on the surface of the 

 a({uarium, and generally remain in this po.sition for 

 some time. The attachment appears jirincipally to 

 be etfected by means of the strong, hook-like spines 

 along the front of the rami of the oars, and partly 

 by the peculiar clavate appendage issuing from 

 the dorsal surface of the head, and which, on close 

 examination, will always be found in immediate 

 contact with the object to wliicli tlie animal is 

 clinging. The animal meanwhile is not alisolutely 

 at rest, for tliere is a slight rhythmical swinging 

 to and fro of the whole body, occasioned by the 

 violent agitation of the branchial legs. These pul- 

 sations take place in exactly the same manner as in 

 the Brant']iipodidæ, not being simultaneous but suc- 

 cessive, thus jirodut'ing the impression of a iicmliai', 



