109 



])aa (let Fig. 5 fremstillede 14 Par ialt. Haledeleii 

 sondrer sig tj-deligere fra Truiictis og Kliver mere 

 onilioiet. Haleklorne er ini bevægeligt artioulerede 

 ])aa S])idsen, og Halepladenie l)eg\-nder at springe 

 stærkere frem. I deres Bagkant viser sig nogle faa 

 tandformige Fremspring, lige.som de oventor Hale- 

 borsterne ndgaaende dorsale Torne begyndor at til- 

 tage i Antal. Hvad den indre Organisation angaar, 

 skal her blot henledes Opmærksomlieden paa den 

 ganske gradvise Udvikling at det i Hovedet liggende 

 leveragtige Organ, der allerede i det sidste af de 2 

 her omhandlede Stadier (Fig. 5) har o])naaet en 

 temmelig com])lireret Bygning. Tjængden af Skallen 

 hos disse 2 Stadier er henholdsvis 1,10 mm. og 2,30 

 mm. Fndnn foregaar der en lignende gradvis Ud- 

 vikling af alle Dele af Legemet indtil Skallen har 

 naaet en Længde af — 7 mm. Da indtrjeder den 

 Iste Hndskiftning inden den )iostlarvale Tilstand, 

 og meget kort Tid efter denne er allerede Individet 

 kjonsmodent, skjont det endnu ne])pe har opnaaet 

 synderlig mere end Halvparten af dets detinitive 

 Storrelse. 



Fig. <) ijaa samme Plani'he fremstiller et Individ 

 nogen Tid etterat denne Hndskiftning er foregaaet 

 Som man ser, har A^alvlerne nn faaet sin forste 

 Væxtstinbe, der lober nogenlunde parallel med og i 

 forholdsvis kort Afstand fra Valvlernes trie Rand. 

 Dannelsen af denne Væxtstribe er ikke vanskelig 

 at forståa. Ved Hudskiftningen bliver nemlig kun 

 den indre Membran af Skallen afkastet, medens den 

 ydre chitinose Lamelle bliver siddende igjen og snji- 

 pleres nu med en nydannet perijther Del. Denne 

 Iste Væxtstribe er altsaa intet andet end Kanterne 

 af de ]n'imære Valvler, der skarjit afgrændser sig 

 fra den efter Hudskiftningen optrædende nydannede 

 Del af Valvlerne. Skallen, der nu har en Længde 

 af 8 mm. og en Hoide af nnn.. har den dorsale 

 Kant jevnt bueformig hoiet, dog langtfra saa stærkt 

 som hos fuhlt udvoxede Individer, og det forreste 

 lljorne er, i Modsætning til hvad TiUældet er hos 

 disse, fuldkommen ligesaa sta'rkt fremtrædende som 

 ilet bagre. Det i Skalli'u indesluttede I )\'r ov i alle 

 Henseender normalt udviklet, alene med den For- 

 skjel, at Braneliialfoddernes Antal er nfiget ringere 

 end hos fuldvoxne E\em]ilaier, nemlig kun 2(1 t\di-- 

 ligt udviklede Far, hvoraf allerede ilde til lite Par 

 har den ovi-e La]i af Exo])o(liten traadformigt for- 

 længet. Til ,'>iderne af Tarmen sees nu tydeligt 

 Ovarienu' meil sine talrig(> Ægfollikler, og i deres 

 indre har allerede afsat sig det ojiakt hvide Seeret, 

 der skal tjene til Dannelsen af Ægka])slerne. Efter 

 nogen Tids Forlob har Individet faaet sin eharac- 

 teristiske Ægmasse under den dorsah' Del af Skal- 

 len. Denne bæres i llegelen af Dyret til næ.ste 

 Hudskittning, da den sammen meil den af kastede 

 Hud bliver ndstodt af Skallen bagtil. Efter Hud- 



functions. In the stage shown in tig. 4. their 

 number is 9 pairs, in that in tig. ry, there are in all 

 14 jiairs. The eandal part is more distinctly divided 

 from the trunk, and becomes more bent d(j\vn\var<ls. 

 The caudal claws are now movably ai-ticnlated at 

 the point, anfi the cauilal lamellæ begin to ])roject 

 nu>re. On their hind margin a few denticular ]>ro- 

 minences appear, while the dorsal .spines issuing 

 from alxjve the caudal setæ, begin to augment in 

 number. "With regard to the internal organisation, 

 attention is here only di'awn to the ver}' gradual 

 development of the hejiatic organ in the head, 

 which, in the latter of the 2 stages here under di.s- 

 cussion (tig. 5), has already attained a tolerably 

 complicated structure. The length of the shell in 

 these 2 stages is res])(«ctively 1.10 mm. and 2.;-50 

 mm. A gradual development of this kind still goes 

 on of all the parts of the body, until the shell has 

 attained a length of oi- 7 mm. Then occurs tlie 

 1st exuviation in the jjost-larval condition, and very 

 shortlv after this, the animal is sexually mature, 

 althfiugh it has scarcely attaim-d more than half 

 its eventual size. 



Fig. on the same ])late. rejiresents an animal 

 some time after this exuviation has taken place. 

 It will be seen that the valves have now ae(|nired 

 their tirst lin(> of growth, which runs almost parallel 

 with, and at a comjtarativeh' short distance from 

 the free edge of the valves. The formation of this 

 line of growth is not difticnlt to understand, for in 

 the exuviation. onl\' the iniu'r membrane of the 

 shell is cast, while the outer cliitinous lamella 

 remains, and receives the addition of a newly-formed 

 peripheral part. This 1st line of growth is thus 

 nothing more than the edges of the prinmry valves, 

 which are sharply defined against the newly-formed 

 portion of the valves appearing after the exuviation. 

 The shell, which now lias a length of S mm. and a 

 height of (1 mm., has its dor.sal edge evenly curved, 

 though not nearly so much as in fully developed 

 sjiecimens; and the iorenu)st corner, unlike that in 

 adult animals, is fully as ])rominent as the hind 

 one. The animal enclosed in the shell is in every 

 respect nornmlly developed, with the one excejition 

 that the branchial legs are rather fewer in number 

 than in adult specimens, there being only 20 dis- 

 tinctly developed pairs, the Uth, 10th and lltli of 

 which already have the filiform elongation of the 

 exopodite. The ovaries with their numerous egg- 

 follicles are now distinctly visible at the .sides of 

 the intestine, and the opai|ue white .secretion to be 

 emploved in thr formation of the egg-capsules has 

 alreadv been deposited inside them. After some 

 time has elapsed, the animal has its characteristic 

 mass tif eggs under the dorsal part of the shell. 

 This is generallv carried by the animal until the 

 next exuviation, when it is cast, together with the 



