48 



har Formen af et ovalt Blad, rundt om besat med 

 en Rad af Fjærbørster. I nogen Afstand fra Exo- 

 poditen, omtrent ved Midten af Stammens Yder- 

 kant, er Epipoditen (ep) fæstet. Den repræsente- 

 res af et forholdsvis ikke meget stort, simpelt, 

 aflangt, sækdannet Vedhæng. der er rettet skraat 

 nedad og bagud. I sin finere Structur skiller den 

 sig noget fra de øvrige Vedhæng, idet den er af 

 mere spongios Beskaffenhed, og antager paa Spiri- 

 tusexemplarer meget snart et temmelig opakt Ud- 

 seende. Foruden de nævnte Hoveddele, som alle 

 ogsaa er tilstede hos Xehalia, kommer her endnn til 

 et særegent Vedhæng, der er specielt eiendomme- 

 ligt for Gruppen Anosfraca, og som jeg ovenfor 

 har benævnt «Dækpladen», for at antyde dets 

 Bestemmelse, der nærmest synes at være den, til 

 en vis Grad at erstatte det manglende E3'gskjold 

 ved at dække over Eoden af Branchialfodderne. 

 Dette Vedhæng (b) udgaar ligeledes fra Ydersiden 

 af Stammen, men lige ved dennes Rod, og har For- 

 men af en meget tynd og gjennemsigtig oval Plade, 

 regelmæssigt sagtakket i Kanterne. — Undersoger 

 man noiere de 11 Par Branchialfndder og sammen- 

 ligner dem med hverandre, vil man finde enkelte 

 mindre Difterentser i deres Bygning. Hvad for det 

 første Størrelsen angaar, saa tiltager de gradvis 

 noget i Længde fra Iste til omtrent 5te Par, for 

 saa jevnt at aftage i Størrelse bagtil, saa at sidste 

 Par neppe er halvt saa stort som 5te og noget min- 

 dre end Iste. Det forreste Par (Fig. 9) skiller sig 

 fra de følgende ved en noget ringere Udvikling af 

 Exopoditen, medens Endopoditen er forholdsvis stær- 

 kere fremspringende, mindre indadrettet, og kun for- 

 synet med en enkelt Torn i Inderkanten. Sidste 

 Par (Fig. 12) udmærker sig fra de øvrige derved, at 

 Epipoditen har antaget Characteren af en tynd 

 Plade, besat i Kanterne med cilierede Borster, og 

 derved at Dækpladen ganske mangler. Endopoditen 

 er paa dette Par meget kort og af afrundet Form, 

 medens Exopoditen er vel udviklet. — Hos Hannen 

 skiller Branchialfodderne (Fig. 13) sig kjendeligt fra 

 samme hos Hnnnen ved Endopoditens betydelig stær- 

 kere Udvikling. Den er navnlig paa de midterste 

 Par stærkt fremspringende indad, næsten af le- 

 dannet Form, og forsynet med et stort Antal af 

 Randtorner. Rimeligvis har denne Modification af 

 Endopoditen hos Hannen et vist Hen.syn til Copula- 

 tionen, idet Branchialfødderne derved delvis kan fun- 

 gere som et Slags Griberedskaber og derved under- 

 støtte 2det Par Antenner i deres Function at fast- 

 holde Hunnen under Parringen. 



movably articnlated to a separate ledge of the stem 

 at the outer side of the endopodite, has the form of 

 an oval lamella, beset all round with a row of plu- 

 mose setæ. At some distance from the exopodite, 

 aboiit in the middle of the outer edge of the stem, 

 the epipodite (ep) is secured. It is represented by a, 

 comparatively, not very large, simple, oblong vesicu- 

 lar appendage, which turns obliquely downwards and 

 backwards. In its microscopical structure it differs 

 somewhat from the other appendages, exhibiting a 

 more spongious character, and in alcoholic specimens 

 it very soon assumes a rather opaque appearance. 

 Besides the above named chief parts, which are all 

 also present in Nehalia, another peciiliar appendage 

 is here added, which particularly distinguishes the 

 group Anostmca, and which I liave named above 

 «the covering plate», in order to indicate its most 

 probable purpose, viz , to replace to a certain 

 extent the absent carapace in covering over the 

 base of the branchial feet. This appendage (b) issues 

 likewise from the outer side of the stem, but close 

 to the base of the latter, and has the form of a very 

 thin and pellucid plate, regularly serrated on the 

 edges. — On a closer examination and comparison of 

 the 11 pairs of branchial feet, some minor differences 

 in their structure will be found to exist. Firstly, as 

 regards the size, they increase successively somewhat 

 in length from the 1st to about the 5th pair, after 

 which thej^ again gradually decrease in size, in such 

 a manner that the last pair are scarcely half as 

 large as the 5th and also somewhat smaller than 

 the 1st. The foremost pair (fig. 9) differ from the 

 succeeding ones by a somewhat slighter development 

 of the exopodite, whereas the endopodite is com- 

 paratively more strongly produced, less incurvate, 

 and only provided Avith a single spine on the inner 

 edge. The last pair (fig. 12) distinguish themselves 

 from the others by the epipodite having assumed 

 the character of a thin plate edged with ciliated 

 bristles, and by the complete want of any covering 

 plate. The endopodite is, on this pair, very short 

 and of rounded shape, whereas the exopodite is well 

 developed. In the male the branchial feet (fig. 13) 

 distinguish themselves very markedly from the same 

 in the female, by the much stronger development of 

 the endopodite. The latter is, especially on the 

 middle pairs, strongly produced inwards, almost 

 falciform in shape, and jjrovided with a great num- 

 ber of marginal spines. In all probability this mo- 

 dification of the endopodite in the male has a cer- 

 tain relation to the act of copulation, since the 

 lirancliial feet thereby become, to a certain extent, 

 enabled to act as a kind of prehensile organs, thus 

 assisting the 2nd pair of antennæ in their function 

 to retain hold of the female dui-ing copulation. 



