102 



med et lidet Indsnit i Enden (f). Ai' de ovenfor 

 beskrevne Lemmer, der alle horer til Hovedet, er 

 det forreste Par udelukkende Føleredskaber, medens 

 de 2 ovrige Par, og navnlig det 2det, er Svømme- 

 apparater, ved hvis Slag forfra bagtil Legemet sted- 

 vis drives frem gjennem Våndet. Bevægelserne er 

 dog i dette Iste Stadium endnu temmelig afbrudte 

 og ubehjælpelige. Forst etterat Larven har under- 

 gaaet sin Iste Hudskiftning, og Svommeborsterne 

 har faaet sin Ciliering, bliver Bevægelserne mere 

 regelmæssige og energiske. Angaaende den indre 

 Organisation, saa lader sig herom lidet eller intet 

 anføre, da der endnu kun synes at være indtraadt 

 en vderst ufuldkommen Ditferentiation af de for- 

 skjellige Væv. 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 bemærkes ofte i Axen 

 af Legemet en svag gulagtig Tone, der kunde synes 

 at antyde Tilstedeværelsen af Tarmroret; men dette 

 er i ethvert Fald endnu ikke tj'deligt afgrændset 

 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- 

 længet 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 iidviklede Dyr. Bagtil har dette Segment en 

 liden Indbugtning og gaar til hver Side af denne 

 ad i en kort indadkrvimmet Fortsats. Hovedets 

 Form er paa det nærmeste uforandret, og ogsaa 

 Lemmerne af en lignende Bygning som hos Iste 

 Stadium, dog med den Forskjel, at alle Svomme- 

 borster paa 2det Par nu er fint eilierede, og at de 

 2 fra Skaftet udgaaende Fortsatser begge har an- 

 taget Formen af stærke, bagudkrummede Borster, 

 hvoraf navnlig den inderste er kraftigt udviklet og 

 tæt cilieret i sit ydre Parti. Ogsaa de 3 laterale 

 Borster paaMandil)ularfodderne er nu grovt eilierede, 

 medens de 3 Endeborster sjnes at mangle Ciliering. 

 Overlæbens terminale Fortsats har forlænget sig 

 adskilligt, saa at den rækker noget ud over Lege- 

 mets bagre Ende. Legemet er endnu fyldt med en 

 lignende amorph kornet Materie som i Iste Stadium, 

 men Tarmroret er dog nu tydligere sondret og viser 

 sig betydelig tykkere fortil end bagtil. Larven, der 

 nu har en Længde af 0,3(5 mm, svømmer temmelig 

 raskt om i Våndet ved rhytmiske Slag af 2det ]^ar 



2 sjiiniform bristles. Tlie 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-de.scribed 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 Lst 

 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 l)ecome more 

 regular and energetic. Concerning the internal 

 organisation there is little or notliing to be said as 

 only an exceedingly imperfect differentiation of the 

 various tissues appears as yet to have taken place. 

 The whole of the bod^', as Avell 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 Lst 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 tlie 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 tiji. this segment has a 

 small sinus, and goes out on eacli 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 tlie 1st stage, 

 yet with the dirterence tliat all tlie natatory bristles 

 on the 2nd pair are now finely ciliated, and that 

 the 2 prdjections issuing from the scape have liotli 

 assumed the shape of strong, backward-curving 

 bristles, of which the inner one is more powerfully 

 developed and tliickly 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 tlie intestinal tube is now more distinctly 

 defined, and appears considerably thicker in front 



