102 
med et lidet Indsnit i Enden (f). Af de ovenfor 
beskrevne Lemmer, der alle horer til Hovedet, er 
det forreste Par udelukkende Foleredskaber, medens 
de 2 ovrige Par, og navnlig det 2det, er Svomme- 
apparater, ved hvis Slag forfra bagtil Legemet stod- 
vis drives frem gjennem Vandet. Bevegelserne er 
dog i dette 1ste Stadium endnu temmelig afbrudte 
og ubehjelpelige. Forst efterat Larven har under- 
gaaet sin Iste Hudskiftning, og Svommeborsterne 
har faaet sin Ciliering, bliver Bevegelserne mere 
regelmessige og energiske. Angaaende den indre 
Organisation, saa lader sig herom lidet eller intet 
anfore, da der endnu kun synes at vere indtraadt 
en yderst ufuldkommen Differentiation af de for- 
skjellige Vev. Hele Legemet ligesaavelsom Lem- 
merne er fyldt med en amorph ensformig kornet Ma- 
terie, der giver Dyret en temmelig opak graalig 
Farve, uden at nogen indre Organer med Sikkerhed 
lader sig paavise. Vistnok bemerkes ofte i Axen 
af Legemet en svag gulagtig Tone, der kunde synes 
at antyde Tilstedeverelsen af Tarmroret; men dette 
er i ethvert Fald endnu ikke tydeligt afgreendset 
fra de omliggende Dele. 
Umiddelbart efter den iste Hudskiftning ser 
Larven saaledes ud som fremstillet Fig. 2 (fra Ryg- 
siden). Det bagre Afsnit af Legemet har nu for- 
lenget sig adskilligt og antaget en mere cylindrisk, 
eller noget konisk Form, og viser i nogen Afstand 
fra Enden en svag Indsnoring, ligesom antydende 
et terminalt Segment, svarende til Haledelen hos 
det udviklede Dyr. Bagtil har dette Segment en 
liden Indbugtning og gaar til hver Side af denne 
ud i en kort indadkrummet Fortsats. Hovedets 
Form er paa det nermeste uforandret, og ogsaa 
Lemmerne af en lignende Bygning som hos Iste 
Stadium, dog med den Forskjel, at alle Svomme- 
berster paa 2det Par nu er fint cilierede, og at de 
2 fra Skaftet udgaaende Fortsatser begge har an- 
taget Formen af sterke, bagudkrummede Borster, 
hvoraf navnlig den inderste er kraftigt udviklet og 
tet cilieret i sit ydre Parti. Ogsaa de 3 laterale 
Borster paa Mandibularfodderne er nu grovt cilierede, 
medens de 3 Endeborster synes at mangle Ciliering. 
Overlebens terminale Fortsats har forlenget sig 
adskilligt, saa at den rekker noget ud over Lege- 
mets bagre Ende. Legemet er endnu fyldt med en 
lignende amorph kornet Materie som i 1ste Stadium, 
men Tarmroret er dog nu tydligere sondret og viser 
sig betydelig tykkere fortil end bagtil. Larven, der 
nu har en Leengde af 0,36 mm, svommer temmelig 
raskt om i Vandet ved rhytmiske Slag af 2det Par 
2 spiniform bristles. The 2nd joint carries one 
such bristle, and the last joint, at its extremity, 3. 
The part of the body lying behind has no trace of 
limbs, and is of an oblong oval shape, with a small 
emargination at the extremity (f). The foremost 
pair of the above-described limbs, all of which belong 
to the head, are exclusively sensory organs, while 
the other 2 pairs, and the 2nd in particular, are 
swimming implements, by whose strokes from front 
to back, the body is driven forward by jerks 
through the water. The movements in this 1st 
stage, however, are still rather intermittent and 
awkward. Only when the larva has undergone its 
first exuviation, and the natatory bristles have 
become ciliated, do its movements become more 
regular and energetic. Concerning the internal 
organisation there is little or nothing to be said as 
only an exceedingly imperfect differentiation of the 
various tissues appears as yet to have taken place. 
The whole of the body, as well as the limbs, is full 
of an amorphous, uniform, granular matter, which 
gives the animal a rather opaque, grayish colour, 
without allowing any of the internal organs to be 
made out with certainty. It is true that in the 
axis of the body a faint yellow tinge may often be 
observed, which might seem to indicate the presence 
of the intestinal tube; but this is at any rate not 
distinctly marked off from the surrounding parts. 
Immediately after the Ist exuviation, the appea- 
rance of the larva is as represented in fig. 2 (from 
the dorsal surface). The hind section of the body 
has now lengthened considerably, and has assumed 
a more cylindrical, or somewhat conical shape, and 
at some distance from the end it exhibits a slight 
constriction, as though indicating a terminal seg- 
ment, answering to the caudal part of the fully- 
developed animal. At the tip, this segment has a 
small sinus, and goes out on each side into a little 
incurved projection. The shape of the head is as 
nearly as possible unchanged, and the structure of 
the limbs is very similar to that in the Ist stage, 
yet with the difference that all the natatory bristles 
on the 2nd pair are now finely ciliated, and that 
the 2 projections issuing from the scape have both 
assumed the shape of strong, backward-curving 
bristles, of which the inner one is more powerfully 
developed and thickly ciliated in its outer part. The 
3 lateral bristles on the mandibular legs are also 
now coarsely ciliated, while the 3 terminal bristles 
seem to be destitute of cilia. The terminal protu- 
berance of the labrum has lengthened considerably, 
so that it extends somewhat beyond the hind 
end of the body. The body is still full of an 
amorphous, granular matter like that in the first 
stage, but the intestinal tube is now more distinctly 
defined, and appears considerably thicker in front 
