26 



smeltede med binandeii og udsendende 2 stærke j 

 Sidestammer, der udbreder sig dels i Brancliial- 

 fadderne, dels i Kroppens Muskulatur, De 4 i Bag- 

 kroppen beliggende G-anglier er betydelig større og 

 ogsaa mere fjernede fra liinanden, med længere og 

 mere tydeligt skilte Commissurer. I Halen løber 

 2 Nervestammer langs ad Bugsiden lige til Hale- 

 grenene, og danner for hvert Par af de smaa Hale- 

 fødder en liden ganglios Opsvulmning. En lignende 

 sj'nes ogsaa at lindes ved Basis af Halegrenene. 



Generationsorganerne. 



Ovarierne er til sine Tider meget let at obser- 

 vere kos det levende Dyr, da de med stor Tydelig- 

 bed skinner igjennem Integumenterne paa Grund af 

 sin intense rødgule Farve. De danner (se Pl. V, 

 Fig. 1, Fig. 2, ov) 2 langstrakte Sække, der stræk- 

 ker sig, til hver Side af Tarmen, igjennem hele 

 Midtkroppen og Bagkroppen og rager endog et 

 Stykke ind i Halen. I enhver af Sækkene findes 

 kun en enkelt Række, sig udviklende Æg, alle med 

 tydelig Kiniblære og grovkornet Blommemasse. Ægge- 

 lederne har det ikke lykkets mig at faa se saa tyde- . 

 ligt, at jeg med Bestemthed kan angive deres Plads. 

 Det har imidlertid forekommet mig. at de udmunder 

 ved Basis af Gte Par Branchialfodder. Testes har 

 omtrent samm^ Beliggenbed som Ovarierne og dan- 

 ner ligesom disse simple Sække, men er betydelig 

 smalere end disse. De munder, ifolge Claus ved 

 Basis af sidste Par Branchialfodder. 



Ud vikling. 



Æggene optages, som ovenfor nævnt, efter at 

 være komne ud af Æglederne, i et Slags Rugehule, 

 der ligger ind under Midtkroppen, omgiven af Ryg- 

 skjoldets Valvler og delvis begrændset af Branchial- 

 fodderne, hvis talrige krummede Endebørster liindrer 

 dem fra at falde ud af Rygskjoldets Hule. De 

 undergaar her sin hele Udvikling, og førsst naar Un- 

 gerne er saa vidt komne, at de med Lethed kan be- 

 væge sig i Våndet, forlader de Klækkehulen. Ud- 

 viklingen er noiere studeret af den russiske Natur- 

 for.sker Kowalewsky, og mine Undersogelser stemmer 

 i alt væsentligt overens med hvad der af denne ud- 

 mærkede For.sker er meddelt. Æggene er Timiddel- 

 bart efter at være optagne i Klækkehulen, af rødgul 

 Farve og noget oval Form. Senere antager de lidt 

 efter lidt en noget lysere Couleur og bliver ogsaa 

 mere gjennemsigtige. De er, som hos Flerheden af 

 Crustaceerne, meroblastiske, idet Størsteparten af 



themselves are relatively small and all alike in 

 size; their 2 halves are completely coalescent Avith 

 each other, and send off 2 powerful lateral stems 

 which distribute themselves partly in the branchial 

 feet and partly in the muscles of the body. The 4 

 ganglia situated in the metasome are considerably 

 larger and also situated farther apart from each 

 other, with longer and more distinctly separated 

 commissures. In the urosome 2 nerve-stems pass 

 along on the ventral side, right to the caudal rami, 

 and form, for each pair of the small caudal feet, a 

 small gangliar swelling. A similar swelling ap- 

 pears also to be present at the base of the caudal 

 rami. 



The reproductive organs. 



The ovaries are at times very easy to observe 

 in the living animal, as they shine through the inte- 

 guments with great distinctness, owing to their 

 intense red-yellow colour. They form (see PI. V, 

 fig. 1, fig. 2, ov) 2 elongate sacs which extend them- 

 selves to each .side of the intestine through the 

 entire mesosome and metasome, and reach even 

 some way into the urosome. In each of the sacs 

 there is found only a single series of developing 

 ova, all having a distinct germinative vesicle and 

 coarsely granular yolk substance. The ovarial 

 ducts I have not been fortunate enough to observe 

 so distinctly that I can with precision state their 

 situation. It has, however, appeared to me that they 

 debouch at the base of the 6th pair of branchial 

 feet. The testicles have nearly the same situation 

 as the ovaries and, like these, form plain sacs, but 

 are considerably narrower than them. According to 

 Claus they debouch at the base of the last pair of 

 branchial feet. 



Development. 



The ova are received, as above stated, after 

 having been discharged from the ovarial ducts, in a 

 kind of hatching cavity, which is situated in below 

 the mesosome. surrounded by the valves of the 

 carapace and partly limited by the branchial feet 

 whose numerous bent terminal bristles prevent them 

 from falling out of the cavity of the carapace. 

 They undergo here their entire development, and 

 first when the young ones have advanced so far 

 that they can move themselves with ease in the 

 water do they abandon the hatching cavity. The 

 development has been closely studied by the Russian 

 naturalist Kowalewsky, and my investigations agree 

 in all material points with what has been stated 

 by that eminent investigator. The ova are, imme- 

 diately after liaving been received into the hatching 

 cavity, red-yellow in colour, and somewhat oval in 

 shape. Subsequently they, little by little, assume 



