107 



rundet Form, med den ovre Kant, livor Valvlerne 

 stoder sammen, næsten ret og endende saavel fertil 

 som bagtil med et tydeligt fremspringende Hjorne. 

 Ovenfra seet (se Fig. 8) viser den sig temmelig 

 l)iiget, idet Breden næsten er lig Hoiden. Til hver 

 Side sees Skalkjertelen med den umiddelbart foran 

 samme liggende Muskelarea med stor Tydelighed, 

 og paa Grund af Skallens store Gjennemsigtighed 

 træder ogsaa den af samme bedækkede Del af Lege- 

 met klart og tydeligt frem. Man kan nu paa Lege- 

 met adskille alle de Åfsnit, som ovenfor er beskrevet 

 lios det voxne Dyr- Dog er Nakkesegmentet endnn 

 temmelig kort, og Truncus kun lidet længere end 

 det forreste Afsnit af Legemet. Hovedet har en 

 fra samme hos det voxne Dyr temmelig afvigende 

 Form. Dets ovre Flade er noget uregelmæssigt 

 hvælvet og endnu iiden Spor af det characteristiske 

 stilkede Fastheftningsorgan, som forst senere dan- 

 nes ved en gradvis Afsnoring af en Del af Hovedets 

 Dorsalparti. Pandedelen er endnn kun lidet frem- 

 springende, og mellem den og det stumpt tilrundede 

 Rostrum er der neppe engang den svageste Indbugt- 

 ning at se. Af Hovedets Vedhæng er Iste Par Fo- 

 lere lidt mere forlængede end hos Larverne, men 

 endnu forholdsvis smaa og uden laterale Lappe. 

 2det Par Folere, eller Aarerne, har, som ovenfor 

 anfort, tabt baade den bagudboiede Borste ved Enden 

 af Skaftet og den tvedelte basale Fortsats. For- 

 ovrigt stemmer de, saavel hvad Skaftets som Gre- 

 nenes Bygning angaar, temmelig nær overens med 

 samme hos Larverne, alene med den For-skjel, at 

 der i Yderkanten af den ovre Gren har udviklet sig 

 en kort Pig, hvoraf intet Spor var at se hos hine. 

 Overlæben er nn betydelig reduceret i Storrelse og 

 har antaget det for det voxne Dyr characteristiske 

 Udseende, idet den lange, dolkformige Endedel er 

 svundet ind til en forholdsvis Iiden tentakelformig 

 Fortsats. Paa Kindbakkerne er der endnu igjen et 

 Riidiment af Mandibularfodderne i Form af et til 

 deres Yderside fæ.stet ubetydeligt koniskt Appendix 

 uden Spor af Leddeling eller Borstebesætning. Bag 

 Kindbakkerne sees de 2 Par Kjæver, som nu, lige- 

 som Kindbakkerne, er i fuld Virksomhed med at 

 bearbeide den optagne Næring. De hos Larven an- 

 lagte 6 Par Branchialfodder er nu functionsmæssigt 

 udviklede, udforende sine characteristiske svingende 

 Bevægelser for Respirationens og Næringsoptagel- 

 sens Formaal, og bag dem er der endnu Anlæg 

 til .3 eller 4 Par nye Fodder. Haledelen er endnu 

 kun svagt omboiet og Haleklorne ufuldstændigt son- 

 drede fra Haleenden. De har hver nær Basis en 

 enkelt kort Sidetand, og ixmiddelbart ovenfor dem 

 udgaar fra Halens Dorsalside 2 meget smaa jevn- 

 sides stillede Fremspring, som forestiller det foi'ste 

 Anlæg til de tandede Haleplader. Ovenfor Hale- 

 borsterne har der endvidere udviklet sig et enkelt 

 Par af de hos det voxne Dyr her forekommende 



valves meet, almost straight, and ending both in 

 front and behind in a distinctly projecting corner- 

 Seen from above (see fig. 8), it appears rather 

 bulging, its bi-eadth being almost equal to its 

 height. On eacli side is seen the shell-gland veiy 

 distinctly, -with the muscular area Ij'ing immediately 

 in front of it; and on account of the great trans- 

 parency of the shell, that part of the body which 

 it covers is seen very clearly and distinctly. All 

 the sections of the body described above in the 

 adult animal, can now be distinguished. The cervi- 

 cal segment, however, is still rather short, and the 

 trunk only a little longer than the foremost section 

 of the body. The head lias a rather diflPerent shape 

 to that in the adult animal. Its upper surface is 

 somewhat irregularly arched, and still without a 

 trace of the characteristic stalked organ of attach- 

 ment, which is formed, but not until later, by a 

 gradual constriction of a part of the dorsal region 

 of the head. The frontal region still projects only 

 slightly, and between it and the bhintly rounded 

 rostrum, there is scarcely even the slightest hollow 

 to be seen. Among the appendages of the head, 

 the first pair of antennæ is a little more elongated 

 than in the larva, but still comparatively small 

 and without lateral lobes. The 2nd pair of antennæ, 

 or the oars, have, as stated above, lost both the 

 backward-curved bristle at the end of the scape and 

 the bifid basal projection. In other respects they 

 agree very closely, as regards the structure of both 

 the scape and the rami, with those limbs in the 

 larva, with the one difference that in tlie outer 

 margin of the upper ramus a short spike has deve- 

 loped, of which there was no trace in the larva. 

 The labrum is now considerably reduced in size, 

 and has assumed the appearance characteristic of 

 the adult animal, the long, ensiform terminal part 

 having shrunk into a comparatively small, tenta- 

 cular projection. Tliere is still a rudiment of the 

 mandibular legs left on the mandibles in the form 

 of an indistinctly conical appendage, — without a 

 trace of articulation or bristles, — attached to their 

 outer side. Behind the mandibles are seen the 2 

 pairs of maxillæ. which now, like the mandibles, 

 are in full activity, manipulating the food admitted. 

 The 6 pairs of branchial legs commenced in the 

 larval stage are now able to perform their function, 

 executing their characteristic swinging movements 

 for the purpose of respiration and the admission of 

 food; and there are the rudiments of 3 or 4 pairs 

 of new legs. The caudal part is still only slightly 

 bent down, and the caudal claws imperfectly- marked 

 ofi' from the end of the tail. They each have near 

 the base a single, short, lateral tooth, and imme- 

 diately above them, tliere issue from the dorsal 

 side of the tail 2 very small juxtaposed projections, 

 representing the earliest rudiment of the dentated 



