105 



tydeligt sondrede, idet der mellem dem ogsaa dor- 

 salt er en temmelig dyb Indbngtning. Hovedet er 

 jævnt livælvet oventil og afrundet fortil, med et 

 stumpt Fremspring nedenfor det enkle Øie, forestil- 

 lende Anlægget til Rostrum. "Umiddelbart bag dette 

 Fremspring sees de endnu knudeformige Iste Par 

 Folere at udgaa. Bag disse igjen rager den enormt 

 udviklede Overlæbe frem, med sin skraat nedad- 

 rettede pigformige Endefortsats. Ved dennes Ba'sis 

 er der indad en liden cilieret Lap, der sædvanligvis 

 er boiet ind mod Mundaabningen og som svarer til 

 den verticalt stillede Endelamelle hos det voxne 

 Dyr. Til Hver Side af Mundaabningen sees de nu 

 vel udviklede Kindbakker, fra hvis ydre Side Man- 

 dibularfodderne udgaar, og umiddelljart bag dem 

 igjen viser sig Anlægget til de 2 Par Kjæver. Ryg- 

 skjoldet Imr nu udviklet sig til en kappeformig 

 Hudduplieatur, bestaaende af 2 .symetriske Halvdele 

 skilte bagtil i Midten ved en dyl) Indbngtning. 

 Det har nu tydeligt sondret sig ogsaa fortil; men 

 de 2 Halvdele gaar ganske umærkeligt over i hin- 

 anden dorsalt, uden at der endnu er nogen tydelig 

 Sondring af 2 Valvler. De sig udviklende Fodder, 

 der nu fuldstændig dækkes oventil af Rygskjoldet, 

 har Ibrlænget sig til noget polseformige Fortsatser, 

 der er rettede skraat bagtil og ligger tæt sammen. 

 Den bagerste Del af Kroppen er ganske svagt om- 

 bniet mod Bugsiden og begynder at sondre sig som 

 en tydelig Haledel. De terminale Fortsatser viser 

 sig nu klarlig at være identiske med de senere be- 

 vægeligt til Enden af Haledelen indleddede Hale- 

 klor. I nogen Afstand fra dem paa Dorsalsiden har 

 allerede Haleborsterne iidviklet sig; derimod er der 

 endnu ikke noget Spor af de for det voxne Dyr 

 characteristiske tandede Haleplader. Af de For- 

 andringer, der er foregaaet med den indre Organi- 

 sation kan nævnes, at de i tidligere Stadier simple 

 blindsækformige Udvidninger af Tarmens forreste 

 Del har hver sondret sig i en dorsal og en ventral 

 Lap, og at Hjertet har dannet sig i den forreste 

 Del af Truncus. 



Sidste Larvestadium er fremstillet Fig. 7, fra 

 Rygsiden. Legemet har nu en Længde af Ll-i mm. 

 og ligner idethele samme hos de 2 foregaaende Sta- 

 dier, dog med den Forskjel, at Ho vedets Pandedel 

 er noget mere fremspringende, og at Rygskjoldet 

 er betydelig større. Dette sidste dækker nu som 

 en bred Kappe Storsteparten af Truncus tilligemed 

 de til samme hørende Lemmer oventil og har bagtil 

 et dybt Indsnit. Fodderne, hvis Antal fremdeles 

 kun er 6 Par, er endmi fuldstændig ubevægelige, 

 men har nu sondret sig i sine respective Hoved- 

 afsnit, hvoraf navnlig Epipoditerne er meget tyde- 

 lige i Dyrets dorsale Stilling. Fra Enderne af Fød- 

 derne er allerede korte Bor.ster begyndt at spire 



1-4 — G. 0. Sjirs : Fauna Norvegiæ. 



very distinctly deiined, as there is, dorsally too, a 

 rather deep hollow between them. The head is 

 evenly arched above and rounded in front, with a 

 blunt projection below the ocellus, representing the 

 rudiment of the rostrum. Immediately behind this 

 ]5rojection, the still nodiform 1st pair of antennæ 

 are seen to issiie. Behind them again, projects the 

 enormously develo]ied labrum, with its spiniform 

 terminal protuberance directed obliquely downwards. 

 At its base inside, there is a little ciliated lobe, 

 which is usually bent in towards the oral aperture, 

 and which corresponds to the vertically-placed ter- 

 minal lamella in the full-grown animal. On each 

 side of the oral apertiire are seen the now well- 

 developed mandibles, from the oiiter side of which 

 issue the mandil)ular legs, and immediately Ijehind 

 them again, appear the rudiments of the 2 pairs of 

 maxillæ. The carapace has now developed into a 

 hood-shaped cuticular duplicature, consisting of 2 sym- 

 metrical halves, separated behind in the middle by a 

 deep depression. It has also become well deiined 

 in front, but dorsall}^ the two halves run quite 

 imperceptibly into one another, without as yet any 

 distinct division into 2 valves. The developing legs, 

 which are now completely covered above by the 

 carapace, have lengthened into somewhat sausage- 

 shaped protuberances, directed obli(iuely backwards, 

 and lying close together. The hinder part of the 

 body is . very slightly bent down towards the ventral 

 surface, and begins to be marked off' as a distinct 

 caudal part. The terminal projections now show 

 themselves clearly to be identical with the caudal 

 claws subsequently movably articulated to the end 

 of the caudal section. At some distance from them 

 on the dorsal side, the caudal bristles have already 

 developed, whereas there is as yet no trace of the 

 dentated caudal lamellæ characteristic of the adult 

 animal. Among the changes that have occurred in 

 the internal organisation, it may be mentioned that 

 the simple cæcal expansions of the front part of the 

 intestine in earlier stages, have become marked oft' 

 into a dorsal and a ventral lobe, and that the heart 

 has been formed in the anterior part of the trunk. 

 In iig. 7, the last larval stage is represented, 

 seen from the ventral surface. The body now has 

 a length of 1,14 mm., and on the whole resembles 

 that i]i the 2 preceding stages, though with these 

 differences, viz., that the frontal part of the head 

 is rather more prominent, and that the carapace is 

 considerably larger. The latter now covers like a 

 broad mantle the upper portion of the greater part 

 of the trunk and limbs, and has a deep emargina- 

 tion behind. The legs, which still only number G 

 pairs, are as yet quite immovable, biit are now divided 

 into their respective principal parts, of which no- 

 tably the epipodites are very distinct in the ani- 

 mal's dorsal position. From the extremities of the 



