103 



Følere og delvis ogsaa Mandibularfødderne, hvorved 

 snart Ryg- snart Bugside vendes opad. 



Et noget senere Stadium er fremstillet Fig. 3 

 fra Bngsiden. Larven har nu naaet en Længde af 

 0,47 mm og har Legemets bagre Afsnit end mere 

 forlænget, skjondt fremdeles uden Spor af Lemmer. 

 De terminale Fortsatser, som aabenbart svarer til 

 Haleklorne hos det voxne Dyr, har strakt sig be- 

 tydeligt i Længde og er skilt ved et dybt Lidsnit, 

 i hvis Bund Analaabningen er beliggende. I det 

 indre af Overlæben sees flere meget tydelige celle- 

 agtige Legemer, aabenbart af kjei-telagtig Natur, og 

 dens terminale Fortsats er nu fnldkommen saa lang 

 som den proximale Del af Overlæben og skraat 

 nedadrettet. Mandibularfoddernes Rodstykke har 

 sondi'et sig skarpere fra Legemet og forlænget sig 

 indad mod Mnndaabningen, livorved det nu meget 

 tydeligt viser sig at repræsentere Kindbakkernes 

 Corpus. Selve Lemmerne synes dog ikke at have 

 undergaaet nogen væsentlige Forandringer i sin 

 Structur. Legemet er i dette Stadium betydelig 

 mere gjennemsigtigt end i de 2 foregaaende Stadier 

 og næsten vandklart, saa at den med gulfarvet 

 Indhold fyldte Tarmkanal med stor Tydelighed 

 skinner igjennem de tynde Integumenter. 



Fig. 4 fremstiller (fra Rygsiden) et betydelig 

 senere Stadium, som er nærved at skifte Hud. Lar- 

 ven har nu en Længde af 0,65 mm. og har under- 

 gaaet flere væsentlige Forandringer. Legemet er 

 idethele temmelig langstrakt, og det bagre Afsnit, 

 uden at regne de terminale Fortsatser, dobbelt saa 

 langt som det forreste, fra hvilket det er sondret 

 ved en meget tydelig Indknibning. I det indre af 

 Hovedet viser sig nu det forste Spor af de sammen- 

 satte Øine i Form af 2 smaa, endnu vidt adskilte 

 Pigmentpletter, der ligger til hver Side og noget 

 ovenfor det enkle Øie. LerebouUet har ment, at de 

 sammensatte Øine dannedes ved en Afspaltning fra 

 det enkle Øie, hvad der er aldeles urigtigt. De 

 dannes ganske uafhængigt af det enkle Øie, der 

 baade hvad Størrelse og Form angaar, er fnldkom- 

 men uforandret. Af Lemmerne er Iste Par fnld- 

 kommen af samme Udseende som hos de tidligere 

 Stadier, men synes at være rykkede noget længere 

 ned paa Bugsiden. Paa 2det Par har den basale 

 Fortsats klovet sig i Enden i 2 borsteformige, tæt 

 cilierede Spidser, og den bagre (iren har faaet en 

 Svømmebørste flere paa Spidsen. Mandibularfødderne 

 viser nu alle sine 3 Led meget tydeligt begrændsede, 

 og den fra næstsidste Led udgaaende Børste har 



than beliind. The larva, which is now 0.36 mm. in 

 length, swims about with tolerable rapidity in the 

 water, with rhythmical strokes of the 2nd pair 

 of antennæ, and partly of the mandibular legs, 

 whereby now the dorsal, now the ventral surface is 

 turned uppermost. 



A somewhat later stage is represented in fig. 3, 

 from the ventral surface. Tlie larva has now 

 attained a length of 0.47 mm and has the posterior 

 section of the body even more elongated, though 

 still without a trace of limbs. The terminal pro- 

 jections, which evidently answer to the caudal claws 

 in the adult animal, have increased considerably in 

 length, and are separated from each other by a 

 deep emargination, at the bottom of which the anal 

 aperture is situated. Inside the labrum are visible 

 several very distinct cellular bodies, evidently of a 

 glandular nature; and its terminal projection is 

 now fully as long as the proximal part of the 

 labriim, and directed obliquely downwards. The 

 basal part of the mandibular legs has become more 

 sharply divided from the body, and is jirodueed 

 inwards towards the oral aperture, thereby showing 

 very clearly that it represents the body of the 

 mandibles. The limbs themselves, however, do not 

 seem to liave undergone any essential change in 

 their structure. The body in this stage is consider- 

 ably more transparent than in the two preceding- 

 stages, being almost as clear as water, so that the 

 intestinal canal, with its yellow-coloured contents, 

 shows with great distinctness through the thin 

 integuments. 



Fig. 4 represents (from the ventral surface) a 

 very much later stage, when the animal is about 

 to cast its skin. The larva now has a length of 

 0.65 mm., and has undergone several important 

 changes. The body is on the whole rather elon 

 gated, and the posterior section, not including the 

 terminal projections, is twice as long as the ante- 

 rior, from which it is separated by a very distinct 

 contraction. Inside the head, the earliest traces of 

 the compound eyes now appear in the shape of two 

 small, and as yet widely-separated spots of pigment, 

 lying one on each side, and somewhat above the 

 ocellus. LerebouUet thought that the compound 

 eyes were formed by a splitting off" from the 

 ocellus, a theory which is altogether incorrect. 

 They are formed quite independently of the ocellus, 

 which, both as regards .size and shape, is altogether 

 unchanged. The 1st pair of limbs is of exactly the 

 same appearance as in the earlier stages, but they 

 seem to have moved a little farther down on the 

 ventral surface. In the 2nd pair, the basal projec- 

 tion has divided at the end into 2 bristle-like, thickly 

 ciliated points, and the posterior ramus has acquired 

 another natatory bristle at the point. The man- 

 dibular legs now show all their 3 joints very 



