104 



antaget en pigformig Character, dannende den umid- 

 delbare Fortsættelse af Leddet. Den terminale Fort- 

 sats af Overlæben, ligesom de nu stærkt forlængede 

 Halefortsatser viser sig rundtom tæt besatte med 

 korte Pigge. Paa det bagre Afsnit af Legemet be- 

 mærkes de forste Ånlæg til Fvygskjoldet og til de 

 < i forreste Par Fodder. Alle disse Dele er dog endnu 

 dækkede af Larvehuden, som uden nogensombelst 

 Afbrydelse strækker sig over dem. Rygskjoldet 

 {den senere Skal) har Formen af 2 smaa, endnu ikke 

 med hinanden dorsalt forbundne afrundede Folde 

 helt fortil, i hvis Indre den forste Antydning til 

 Skalkjertelen lader sig paavise. Fodderne har endnu 

 kun Udseende af en Række af G ubetydelige knop- 

 formige Fremspring langs Siderne af Kroppen umid- 

 delbart bag Anlægget til Rygskjoldet. De aftager 

 successivt i Storrelse bagtil, og de 2 sidste Par er 

 kun meget svagt antydede. I det indre af det sær- 

 deles gjennemsigtige Legeme sees nu Tarmkanalen 

 med stor Tydelighed. Den har bagtil sondret en 

 vel begrændset, stærkt muskulos Endetarm, og gaar 

 fortil ud i 2 korte blindsækformigeUdvidninger: den 

 første Begyndelse til den senere saa complicerede 

 Lever. De forskjellige Muskler, der tjener til 

 Aarernes og Mandibularfoddernes Bevægelse kan nu 

 med stor Tydelighed adskilles, og Larven bevæger 

 sig ogsaa i dette Stadium adskilligt mere euergiskt 

 end i de tidligere. 



I det næste her afbildede Stadium (Fig. 5) har 

 Larven en Længde af 0,87 mm, og viser en videre 

 Udvikling af det bagre Afsnit af Legemet, som nu, 

 inclusive de terminale Forsatser, er over 3 Gange 

 saa langt som det forreste. De Dele, der paa fore- 

 gaaende Stadium, viste sig umiddelbart indenfor 

 Larvehuden, nemlig Rygskjoldet og de 6 Par Fod- 

 knuder, træder nu alle frit frem fra Legemets Over- 

 flade og har tiltaget noget i Storrelse. De sammen- 

 satte Øine er ligeledes betydelig .storre og er ryk- 

 kede noget nærmere sammen, skjondt de endnu er 

 skilte i Midten ved et tydeligt Mellemrum. Ethvert 

 af dem er nu omgivet af en klar Bræm, hvori senere 

 de enkelte Synselementer udvikler sig. I Rj'gningen 

 af de 3 Par oprindelige Nauplius-Lemmer viser ikke 

 Larven nogen væsentlige Forskjelliglieder fra samme 

 1k)s det sidst beskrevne Stadium. En Føler af Iste 

 Par er af bildet meget stærkt forstørret Fig. ba; 

 den viser, som det vil sees, fuldkommen det samme 

 rudimentære Udseende som lios de yngste Larver. 



Fig. fremstiller en Larve i et senere Stadium, 

 seet fi'a venstre Side, mod den tilsvarende Aare 

 udeladt, for at vise de ai' denne dækkede Dele af 

 Hovedet tydeligere. Larvens IjU'ngde er lidt over 

 1 mm. De, 2 Afsnit af Ijegemet viser sig meget 



distinctly defined, and the bristle projecting from 

 the last joint but one has acquired a spiniform 

 character, forming the immediate continuation of 

 the joint. The tei-minal ])rotuberanee of the labruni, 

 as also the now greatly elongated caudal projections, 

 appear thicldy covered all round with short spines. 

 On the posterior section of the body, the earliest 

 rudiments of the carapace and of tlie (i foremost 

 pairs of legs are observable. All these parts, how- 

 ever, are still covered by the larval skin, which is 

 stretched over them without any interruption Avhat- 

 ever. The carapace (the future shell) is in the 

 shape of 2 small, rounded folds right in front, and 

 not connected dorsally with one another, inside 

 which the earliest indication of the shell-gland may 

 be made out. The legs have still only the appea- 

 rance of a row of (J small, bud-like projections 

 along the sides of the body, immediately behind 

 the rudiment of the carapace. They diminish in 

 size successively behind, and the last 2 pairs are 

 only very faintly indicated. Li the interior of the 

 exceedingly transparent body, the intestinal canal 

 is now seen with great distinctness. Po.steriorly, 

 a well-defined, vei'v muscular rectum has been di- 

 vided oft', and in front, it forms 2 short cæcal expan- 

 sions, — the earliest commencement of the subse- 

 quently so comjilicated liver. The ditt'erent muscles 

 employed in the motion of the oars and the mandi- 

 bular legs, can now be very clearly distinguished, 

 and the larva moves much more energetically in 

 this stage than in tlie earlier ones. 



In the next stage represented here (fig. 5) the 

 larva has a length of 0.87 mm. and exhibits a 

 further development of the posterior section of the 

 body, which now, including the terminal projections, 

 is more than 3 times as long as the anterior sec- 

 tion. Those parts which in the preceding stage 

 appeared immediately within the larval skin, viz. 

 the carapace and the U pairs of pedal buds, now 

 all project freely from the surface of the body, and 

 have somewhat increased in size. The compound 

 eyes are also considerably larger, and have moved 

 a little nearer together, though they are .still sepa- 

 rated in the middle by a distinct space. They are 

 both surrounded by a clear rim, in which the visual 

 elements are subsequently developed. In the struc- 

 ture of the 3 pairs of original nauplius limbs the 

 larva presents no essential difterence from those in 

 the last-described stage. One antenna of the 1st 

 pair is shown, very highly magnified, in fig. 5 a; 

 as will be seen, it presents exactly the same rudi- 

 mentary appearance as in the youngest larva. 



Fig. (J represents a larva in a later stage, seen 

 from the left side, with the left oar omitted in urder 

 to show more distinctly those ])arts of the head 

 which it covers. The length of the larva is a little 

 over 1 nun. MMie 2 sections of the body appear 



