77 



Indre Organer. 



Fordøielsessystemet. — Tarmen danner i^se Tab. 

 XIII, Fig. \, '2) et .simpelt og temmelig vidt, bagtil 

 noget afsmalnende Ror, der strækker sig igjennem 

 Axen af Legemet, og udmnnder, etterat liave dan- 

 net en kort Endetarm, ved Enden af sid.ste Hale- 

 segment, nnder Ba.«is af Halepladen. Paa Under- 

 siden af dens forreste sti;mpt afrundede Del mnnder 

 Spiserøret, der er stærkt mnsculost og stiger lodret 

 i Veiret fra Mnndaabningen. .Dets ovre Ende seirin- 

 ger frit frem i Tarmens Liamen, og viser lier en 

 eiendommelig klapformig Indretning (se Tali. XII, 

 Fig. 10, 11, æ), hvorved Tarmens (."ontenta hindre.s 

 fra at passere tilbage ind i Spiseroret. Med den 

 forreste Del af Tarmen forbinder sig et meget rom- 

 pliceret leveragtigt Oi'gan, der tylder en stor I)el af 

 Hovedet (se Tab. XIII, Fig. 1, 2, 1). Det bestaar 

 af 2 .symetriske Halvdele, hver delt i talrige nregel- 

 mæssigt forgrenede Blindsække (Fig. o), der er ud- 

 klædt indvendig med et Lag af glandulose Celler. 

 Alle disse Blindsække samler .sig tilsidst paa hver 

 Side til en fælles kort Stamme, der mnnder i den 

 forreste Del af Tarmen. Det hele Apparat svarer 

 ntvivlsomt til de 2 forholdsvis simjile lilindsæk- 

 fbrmige Udvidninger af Tarmen lios Branrhipodi- 

 derne. 



Karsystemet. — Hjertet (Fig. L 2, <■) er af me- 

 get langstrakt Form, og strækker sig igjennem liele 

 Midtkro])pen, fra Mandibularsegment og ind i Ilte 

 fodbærende Segment. Som sædvanligt, ligger det 

 \imiddelbart ind nnder Krojipens dorsale Integument, 

 og afsmalnes gradvis forfi'a bagtil, hvor det synes 

 at ende blindt. Fortil har det derimod en vid Aab- 

 ning, hvorigjennem Blodet drives nå i Hovedet og 

 derfra i ll_ygskjoldet og den øvrige Krop. For hvert 

 Kropssegment har det et Par venose Spalter, for- 

 synede med 2 klapformige, bevægelige Læber, der 

 afvexlende lukker og aabner sig, og hvorimellem 

 Blodet optages i Hjertet fra de forskjellige Dele af 

 Legemet. I Rygskjoldet finder en meget livlig Blod- 

 firculation Sted, og Blodet gjennem strømmer lier et 

 meget com])liceret System af Hulrnni, beliggende 

 mellem de 2 Lameller, hvoraf R3'gskjoldet er sam- 

 mensat. Nogen virkelige Blodkar existerer imidler- 

 tid ligesaalidt her som hos andre Pliyllo]icider. 



Nervesystemet. — Som hos andre Krebsdyr, be- 

 staar Nervesy.stemets Centra Idele af det ovre Svælg- 

 ganglion, eller Hjernegangliet, og en Bugganglie- 

 kjæde. Hjernegangliet er meget vanskeligt at un- 

 dersoge, da det ligger tæt omhyllet af andre Dele. 

 Saavidt jeg haj- kunnet se ved omhyggelig Dissec- 

 tion, er det (Tab. XIII, Fig. 5, g) forholdsvis lidet 

 og af betydelig simplere Bygning end hos Branchi- 

 podiderne, uden de hos disse forekommende dorsale 



Internal Organs 



Digestive system. — The intestine (see Pl. XIII, 

 figs. 1, 2) is in the form of a simple, rather wide 

 tnlje, slightly ta]iering posteriorly, and extenrl^ng 

 through the axis of the body; after having formed 

 a short rectum, it 0])ens at the end of the last 

 caudal segment beneath the base of the caudal 

 lamella. On the under side of its anterior, bluntly- 

 rounded part, (i])ens the (esophagus, which is excee- 

 dingly muscular, and rises perpendicularly from the 

 oral aperture. Its upper end projects freely into 

 the lumen of the intestine, exhibiting there a pecu- 

 liar valve-like arrangement (see PI. XII, figs. 10, 

 11, (e), wherein* the contents of the iiite.stine are 

 prevented from passing back into the (esophagus. 

 With the foremost part of the intestine is connected 

 a vei'v complicated hepaticous organ, which occupies 

 a great part of the head (see Pi. XIII. figs. 1, 2. 1). 

 It consists of 2 symmetrical halves, each divided 

 into numerous irregularly ramified cæca (fig. 3), 

 which are lined interiorly with a stratum of glan- 

 dular cells. All these cæca unite at last, on each 

 side, into a slif)i't common stem that opens into the 

 anterior part of the intestine. The whole apparatus 

 undoubtedly answers to the two comparatively 

 simple cæcum-like expansions of the intestine in 

 the Branchipodidæ. 



Vascular system. — The heart (fig. 1, 2, c) is 

 of a very elongated shape, and extends throughout 

 the mesosome, from the mandibular segment into 

 the nth pedigerous segment. It lies, as usual, imme- 

 diately below the dorsal integument of the body, 

 and tapers gradually from the front to tlie back, 

 where it seems to have no outlet. In front, on tlie 

 contrary, it has a wide opening, through which tlie 

 blood is driven out into the head, and thence into 

 the carapace and the rest of the body. In each 

 segment of the mesosome there are two venous 

 o.stia, each furnished with 2 valve-like movable lips, 

 which alternately open and shut, and through which 

 the blood is received into the lieart from the dift'e- 

 rent parts of the bod\-. A very active circulation 

 takes place in the carapace, the blood flowing 

 through a ver\' comjilicated system of cavities lying 

 between the 2 lamellæ of which the carapace is 

 composed. Actual blood-vessels, however, no more 

 exist here than in other Phyllopoda. 



Nervous system. — As in other crustaceans, the 

 central ])ortion of the nervous .system consists of an 

 upper (esophageal ganglion, or cereliral ganglion, and 

 a ventral ganglion chain. The cerebral ganglion is 

 very difficult to examine, as it is closely enveloped 

 by other parts. As far as I have been able to see 

 by careful dissection, it is comparatively small (PI. 

 XIII, fig. 5, g), and of a much simpler structure 

 than in the Branchijiodidæ, without the dorsal lobes 



