97 



bagerste Strom. Begge modes ved det dorsale Liga- 

 ment, hvor de boier om iiidad og tidtommer sit Blod, 

 sammen med det fra Hovedet tilliagevendende, i den 

 forreste Del at Hjertet gjennem dettes Iste Par 

 Spaltaalininger. De ovrige 3 Far S}ialtaalininger 

 surnes at optage det Blod, der, etterat have eirculeret 

 i Fodderne, vender tilbage til Hjertet. 



Respirationsapparat. — Eent morphulogiskt maa 

 vistnok Foddernes Epipoditer ansees som de egent- 

 lige Respirationsorganer, da de aabenbart svarer til 

 Gjellerne hos hoiere Krebsdyr. Men da ogsaa de 

 ovrige Dele at Fodderne viser en lignende over- 

 maade delikat Struktur, har man Grund til at an- 

 tage, at Res])irationen ikke er udelukkende ind- 

 ski'ænket til hine Vedhæng, men foregaar overalt 

 paa Foddernes Overtlade, hvad der ogsaa liar givet 

 Anledning til den almindelig benyttede Benævnelse 

 Branchialfodder. Som det phvsiologiskt vigtigste 

 Respirationsorgan maa vi dog ntvivlsomt anse selve 

 Skallen, i hvilken der, som ovenfor anfort, tinder 

 en meget livlig Blodcirculation Sted. Ved Foddernes 

 rhytmiske Bevægelser sker der nemlig en stadig For- 

 nyelse af Våndet indenfor Skallen, og da dette Vand 

 umiddelliart lieskyller den særdeles delikate Mem- 

 bi-an, der beklæder Valvlerne indvendigt, synes alle 

 Betingelser at være tilstede for at en hurtig Gas- 

 rxdvexling her kan .ske med det indenfor Membranen 

 stromniende Blo(l. 



Nervesystemet. — Den i Hovedet beliggemle 

 Del af Nervesysteniet er ikke vanskelig at obser- 

 vere paa tilstrækkelig gjennemsigtige Exemplarer. 

 Den bestaar af det saakaldte ovre Svælgganglion, 

 eller Hjernegangliet, med de fra samme udgaaende 

 Nerver. Selve Hjernegangliet er ikke af særdeles 

 betydelig Størrelse, og ligger (se Tab. XV, Fig. 2) 

 temmelig langt tilbage i Hovedet, umiddelbart bag 

 det enkle Øie, hvoi-med det forbinder sig med en 

 temmelig bred Fortsats (se ogsaa Tab. XVI, Fig. '.', 

 lOl Det liestaar, som sædvanlig, af 2 symetriske, 

 med hinanden i Midtlinien forbundne Halvdele, 

 hvoraf enhver er udtrukket i 2 divergerende, koni- 

 ske Fortsatser. Fra de forreste Fortsatser iidgaar 

 de overordentlig lange og stærke Synsnerver og 

 desuden en ganske liden Nerve for (Jiemusklerne. 

 Selve Synsnerverne jiasserer fnrtil ind i Hovedets 

 Pandedel, hvor enhver af dem svulmer ud til et 

 kolleformigt Synsganglion. Begge Ganglier ligger 

 tæt sammen, uden dog at smelte sammen, og deres 

 Ender er kun ubetydeligt fjernet fra de sammen- 

 satte Øine (se Fig. 10). Fra dem udgaar talrige 

 line Nervefibre, der trænger ind i Oinene og for- 

 binder sig med disses enkelte Synselementer. De 

 bagre Fortsatser af Hjeimegangliet (a ') er noget 

 kortere end de forreste og mere udadrettede (se Fig. 

 10), men af en lignende konisk Form. De giver 



13 — G. 0. Sårs: Fauna Korvegix. 



anterior stream, and one considerably longer ])os- 

 terior one. They meet at the dorsal ligament, where 

 they turn inwards, and empty their Ijlood, together 

 with that running back from tlie liead, into the an- 

 terior ]iart of the heart through that organ's tirst 

 pair of ostia. The 3 other pairs of ostia appear to 

 receive the l^lood whicli, after having cii'culated in 

 the legs, returns to the heart. 



Respiratory Organs. — From a purely morpho- 

 logical piiint of view, the epipodites of the legs 

 must be considered as the true respiratory organs. 

 as they evidently answer to the gills in higher 

 Crustaceans. But as the other parts of the legs 

 also show a similar exceedingly delicate structure, 

 there is reason to suppose that the function of 

 respiration is not confined exclusively to these 

 apjiendages, but is carried on over the entire sur- 

 face of the leg, a circumstance which has given rise 

 to the generally used term — branchial legs As 

 the physiologicalh' most important organ of re.spi- 

 ration however, we must undoubtedly regard the 

 shell itself, in which, as stated above, a very active 

 circulation of the blood goes on. By the rhythmical 

 movements of the feet, a constant renewal of the 

 water inside the shell takes place, and as this water 

 is in immediate contact with the peculiarly delicate 

 membrane lining the interior of the valves, all the 

 conditions requisite for a rapid exchange of gas 

 with the blood flowing within the memlirane, ajqiear 

 to be present. 



Nervous System. — That part of the nervous 

 system lying in the head is not difficult to observe 

 in sufficiently transparent specimens. It consists 

 of the so-called supra-æsophageal ganglion or cere- 

 bral ganglion, with the nerves proceeding from it. 

 The cerebral ganglion itself is of no very consider- 

 able size, and is situated (see PI. XV, fig. 2) rather 

 far back in the head, immediatel\' l)ehind the ocel- 

 lus, with which it is connected hy a tolerably 

 broad projection (see also PI. XVI, figs. 9, 10). It 

 consists as usual of 2 symmetrical halves connected 

 with one another in the median line, each half 

 being drawn out into 2 divergent conical protuber- 

 ances. From the foremost of these issue the excee- 

 dingly long and strong optic nerves, as also a very 

 small nerve for the ocular muscles. The optic 

 nerves themselves ])ass forwards into the frontal 

 part of the head, where they each swell out into a 

 club-like optic ganglion. These ganglia lie close 

 together witliout however coalescing, and their 

 extremities are at only a slight distance from the 

 compound eyes (see fig. 10). Numerous delicate 

 nerve-filires issue from them, entering the eyes, and 

 connecting themselves with the several visual ele- 

 ments of those organs. The hind protuberances (jf 

 the cerebral ganglion (a') are ratlier shorter than 

 the front ones, and directed more outwards (see 



