frem, og, sees Dyret fra Bugsiden, lader ogsaa 
Coxallappene sig tydeligt adskille. De sammensatte 
Qine er nu rykkede ner sammen, og i den periphere 
Area har allerede Synselementerne begyndt at danne 
sig. Larven beveger sig om i. Vandet paa fuld- 
kommen samme Maade som i tidligere Stadier. Be- 
vegelsen tilveiebringes hovedsageligt ved 2det Par 
Folere eller Aarerne, ved hvis rhytmiske Slag for- 
fra bagtil Legemet drives frem gjennem Vandet paa 
en eiendommelig stodvis Maade. Ved hvert Slag af 
Aarerne fores deres basale indadkrummede Fortsats 
ind mellem Overleben og Kroppen, saa at de 2 
borsteformige Spidser kommer i Contact med Mund- 
regionen, og det synes derfor som om denne Fort- 
sats har en vesentlig Betydning ved Neringsopta- 
gelsen. lLarvetilstanden er nu endt, og med den 
umiddelbart folgende Hudskiftning begynder den 
2den Periode i Dyrets Udvikling, den postlarvale 
Tilstand. 
Postlarval Udvikling. — Fig. 8, 9 fremstiller 
Iste postlarvale Stadium, hvilket folger umiddelbart 
paa det ovenfor beskrevne sidste Larvestadium, idet 
kun en enkelt Hudskiftning betegner Grendsen 
mellem begge. Og dog viser Dyret nu et totalt 
forskjelligt Udseende, ligesom dets Maade at bevege 
sig paa er meget afvigende. Man har nu ikke syn- 
derlig Vanskelighed ved i det at erkjende en ung 
Limnadia, skjondt der endnu er tilbage nogle Spor 
fra Larvetilstanden.- Hyad der vesentlig charac- 
teriserer dette Stadium ligeoverfor Larvestadierne, 
er den betydelige Udvikling af Rygskjoldet, som nu 
har omformet sig til en tydeligt tveklappet Skal, 
der bedekker Storsteparten af Legemet, ikke blot 
oventil, men ogsaa til Siderne. Skallen er dog 
endnu ikke saa stor, at Legemet kan fuldstendig 
inddrages i samme, saaledes som Tilfeeldet er med 
fuldt udviklede Exemplarer, og Hovedet, ligesom 
ogsaa Halen er derfor altid ubedekkede. En anden 
veesentlig Forandring bestaar i Reductionen af Man- 
dibularfodderne og den fuldsteendige Mangel af de 
2 fra Aarernes Skaft udgaaende bagudboiede Fort- 
satser. Endelig maa anfores som en veesentlig Cha- 
racter, at de hos Larven fuldkommen ubevegelige 
Branchialfodder nu er traadt i Virksomhed, ud- 
forende sine rhytmiske svingende Bevegelser. Leeng- 
den af Legemet, maalt fra Panden til Enden af 
Haleklorne er 1,14 mm, eller noiagtig den samme 
som hos Larven i sidste Stadium. Men medens Skal- 
len hos dette sidste Stadium kun var 0,40 mm. lang 
og neppe mere end halvt saa hoi, har den nu en 
Lengde af 0,70 mm. og en Hoide af 0,60 mm. Den 
er ganske klar og. gjennemsigtig, uden Spor af de 
hos voxne Exemplarer forekommende concentriske 
Linier, ligesom Formen er noget afvigende. Seet 
fra Siden (se Fig. 9) viser den en-uregelmessig af-_ 
106 
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‘ner as in the earlier stages. 
legs, short bristles have already begun to shoot 
forth, and when the animal is seen from the ventral 
surface, the coxal lobes may also be distinguished 
clearly. The compound eyes have now moved close 
together, and in the peripheral area the visual ele- 
ments have already begun to form. The larva 
moves about in the water in exactly the same man- 
The movement is 
brought about chiefly by the 2nd pair of antenne 
or the oars, by whose rhythmical strokes from front 
to back the body is propelled through the water in 
a peculiar, jerky manner. At each stroke of the 
oars, their basal, incurved projection is carried in 
between the labrum and the body, so that the 
2 bristle-like points are brought into contact with 
the oral region. It therefore seems as though this 
projection was of essential importance in the admis- 
sion of food. The larval condition is now termi- 
nated, and with the immediately succeeding exuvia- 
tion begins the 2nd period in the animal’s develop- 
ment, the post-larval condition. 
Post-larval Development. — Figs. 8 and 9 repre- 
sent the first post-larval stage, which follows imme- 
diately after the above-described last larval stage, 
only a single exuviation marking the boundary be- 
tween the two. And yet the animal now presents 
a totally different appearance, its manner of moving 
being also very different. There is very little diffi- 
culty now in recognising in it a young Limnadia, 
although there are still some traces left of its larval 
-condition. What principally characterises this stage 
as compared with the larval stages is the consider- 
‘able development of the carapace which is now 
‘transformed into a distinctly bi-valved shell, cover- 
-ing the greater part of the body, not only above, 
but also at the sides. The shell, however, is not yet 
so large as to allow of the body being completely 
withdrawn into it, as is the case with fully deve- 
loped animals; the head therefore, and the tail are 
always uncovered. Another essential change con- 
sists in the reduction of the mandibular legs and 
the total absence of the 2 backward-curved projec- 
tions from the scape of the oars. Lastly, it must 
be mentioned as an essential character that the 
quite immovable branchial legs in the larva have 
now begun to act by performing their rhythmical, 
swinging movements. The length of the body, mea- 
sured from the frontal part to the end of the caudal 
claws is 1.14 mm., or exactly the same as that of 
the larva in the last stage. But while the shell in 
that stage was only 0.40 mm. long, and scarcely more 
than half as high, it now has a length of 0.70 mm. 
and a height of 0.60 mm. It is quite clear and transpa- 
rent, without a trace of the concentric lines occurring 
in fullgrown animals, and the shape is somewhat diffe- 
rent. Seen from the side (see fig. 9), it shows an irre- 
gular, rounded shape, with the upper margin where the 
