90 



lig ndpræget Sondring af Midtkrop og Bagkrop An- 

 des ikke. Men, i Lighed med hvad vi bar gjort med 

 Lepidums, lader sig maaske Grændsen mellem begge 

 sætte ved det 1 1te Segment, der bærer det bagerste 

 af de 3 Par Brancbialfodder, bvis Exopoditer er om- 

 formede til Fæste for Ægmassen, og hvor ogsaa 

 Kjonsaabningerne har sin Plads. 



Haledelen (se Tab. XVI, Fig. 7) er ganske kort, 

 usegmenteret, og oraboiet mod Bngsiden. Den er i 

 sin forreste Del temmelig tyk, men ndvides bagtil 

 mod Enden til 2 tynde, jevnsidesliggende Plader, 

 der hver nedad springer frem i Form af en tornformig 

 Fortsats. Ovenfor denne Fortsats er Randen af 

 hver Plade delt i et noget vekslende Antal (fra 8 

 til 15) smaa tandformige Fremspring cilierede i Kan- 

 terne. Hvor Pladerne ophorer oventil, er der i Mid- 

 ten en liden Knude, hvorpaa er fæstet 2 fint cili- 

 erede 2-leddede Borster (Haleborsterne), og ovenfor 

 dem igjen er den stærkt convexe, næsten hælformigt 

 fremspringende Rygflade af Halen bevæbnet med 

 omkring 6 stærke bagudboiede Torne, fint tandede 

 i Kanterne, og ordnede i 2 nregelmæssige Rader (se 

 ogsaa Fig. 7, bis). Til den afstumpede Ende af 

 Haledelen er bevægeligt indleddede 2sæx'deles lange 

 og stærke, men kiin gan.ske svagt bøiede Klor (Hale- 

 klorne), der morphologiskt synes at svare til Hale- 

 traadene hos Apodiderne og den saakaldte Fnrca hos 

 Branchipodider og PhyUocarider. De afsmalnes grad- 

 vis med Enden, som gaar ud i en fin Spids, og har 

 langs den bagre, noget concave Side talrige smaa 

 Tagger samt desuden i sin basale Del et Antal af 

 fine Børster. 



De sammensatte Øine (se Tab. XV, Fig. 2, 3, 4, o) 

 har, som ovenfor nævnt, sin Plads i det indre af den 

 koniskt fremspringende Pandedel, hvis stumpt til- 

 rnndede Ende de næsten fuldstændigt ndfylder. De 

 ligger meget nær sammen og stoder endog hos fuld- 

 voxne Individer umiddelbart til hinanden i Midt- 

 linien (se Fig. 3, 4). Seet fra Siden (Fig. 2) har 

 hvert Øie en fuldstændig cirkelrund Form, hvorimod 

 de, ovenfra eller nedenfra seet, viser sig paatværs 

 ovale. Begge Øine er (se Tab. XVI, Fig. 10, o) om- 

 givne af en fælles tynd og gjennemsigtig Membran 

 og bestaar af et meget bet3'deligt Antal af Syns- 

 elementer, hvis ydre Del, som sædvanlig, har For- 

 men af stærkt lysbrydende korte Kegler indplantede 

 med sin Spids i det mørke Øiepigment. Dette sidste 

 har en noget lysere overfladisk Skikt, hvorfor Kry- 

 stalkeglerne in denf or Kanterne afØiet tager sig ved 

 paafaldende Lj's ud som tæt sammen liggende regel- 

 raæssige morke Pletter, medens de i Peripherien 

 danner en klar Bræm, eller Indfatning om Øiet. 

 Øinene er til en vis Grad bevægelige, idet de dels 

 kan trækkes noget tilbage i Hovedet, dels noget 



ment.s being the most highlj- developed. There is no 

 distinctly-marked division of the mesosome and me- 

 tasome ; but as in Lepidurus, we may perhaps place 

 the boundary between the two, at the 11th seg- 

 ment, which carries the hindmost of the 3 pairs of 

 branchial legs whose exopodites are transformed to 

 support the egg-mass, and where, too, the genital 

 openings are situated. 



The caudal part (see PI. XVI, fig. 7) is quite 

 short, unsegmented and curved towards the ventral 

 surface. In its anterior part it is rather thick, but 

 expands posteriorly towards the extremity into 2 thin, 

 juxtaposed lamellæ, each of which pn>jects below in 

 the form of a spiniform prominence. Above this 

 prominence, the margin is divided into a somewhat 

 varying number (from 8 to 15) of small dentiform 

 projections with ciliated margins. Where the lamellæ 

 end above, there is, in the middle, a little tubercle, 

 to which are attached 2 finely-ciliated, 2-jointed 

 bristles (caudal bristles), and above them again is 

 the highly convex, almost heel-like, projecting dorsal 

 surface of the tail, armed with about 6 strong, 

 backward-curved spines, finely dentated at the edges, 

 and arranged in 2 irregular rows (see also fig. 7, bis). 

 To the blunt end of the caudal part, 2 particularly 

 long and strong, but only very slightly curved 

 claws (caudal claws) are movably articulated; they 

 seem, morphologically, to correspond to the caudal 

 filaments in the Apod idee, and the so-called furca in 

 the Brancliipodidæ and PhyUocaridæ. They taper 

 gradually towards the extremity, which is very 

 finely pointed, and along their posterior, somewhat 

 concave side they are clothed with numerous .small 

 teeth, and moreover in their basal part with a 

 number of fine bristles. 



The compound e\-es (see PI. XV, figs. 2, 3, 4, o) 

 are situated, as already mentioned, inside the coni- 

 cally projecting frontal part, almost filling its bluntly 

 rounded end. They lie very close together, and 

 even touch one another in the median line in full- 

 grown animals (see figs. 3, 4). Seen from the side 

 (tig. 2), each eye has a perfectly circular shape, 

 whereas seen from above or below, they appear 

 transversely oval. Both eyes (se PI. XVI, fig. 10, o) 

 are surrounded by a thin and transparent common 

 membrane, and consist of a very considerable num- 

 ber of visual elements, whose oiiter part has, as 

 usual, the shape of short, highly-refractive cones, 

 with their point planted in the dark ocular jjigment. 

 This pigment has a rather lighter superficial coating 

 causing the crystalline cones within the margin of 

 the eye to appear, when the light falls upon them, 

 like closely-adjacent, regular, dark spots, while those 

 in the periphery form a clear rim or setting round 

 the eye. The eyes are movable to a certain extent, 

 being partly capable of slight retraction into the 

 head, ]iartly of being slightly turned on their axis. 



