844 EXPLANATION OF PLATES. 



Fig. 4. The central nervous system of Helix Pomatia L. ; after BRANDT 

 and BATZEBURG Mediz. Zool n. Tab. 34, fig. 12; compare p. 766; 

 1, ganglion situated above the cesophagus; 2, below it. 



Fig. 5. Blood-circulation of Helix Pomatia L.; after CUVIER, as an 

 example of the Pneumonica, p. 811 ; a, heart; c, auricle, both 

 lie in the pericardial sac, laid open ; b, b', arteries ; e, e, venous 

 currents, from which the pulmonary veins in the respiratory 

 cavity arise, which pass into the trunk d that runs to the 

 auricle ; f, f, calcareous sac or kidney which surrounds the peri- 

 cardium. Compare pp. 760, 761. 



Fig. 6. Limax ater L., the anterior portion of the animal, after BRANDT 

 u. BATZEB. op. cit. Tab. 38, fig. 3, (Arion empiricorum brunneus). 

 A, respiratory aperture at the margin of the mantle. See 

 p. 817. 



Fig. 7. Circulation of the blood in a cephalopod mollusc, Loligo, after 

 CUVIER Tabl. elem. de VHist. nat. des Animaux; a, vena cava, 

 which divides into two branches; b, b, lateral or venous hearts; 

 c, c, branchial veins ; d, d, space where the gills are situated ; f, 

 the middle or arterial heart ; g, g, g, arteries. The direction of 

 the current is indicated by arrows. Compare pp. 762 and 819. 



Fig. 8. A small specimen of Sepia officinalis L., p. 829; after CARUS 

 Nov. Act. A cad. Cces. Natur. Curios, xn. ; a, a, a, a, a, a, a, a, the 

 eight conical arms, the two long thin arms are seen at b, bj c, 

 funnel; comp. pp. 818, 819. 



Fig. 9. Detached arm (Hectocotylus) of a male individual of Argonauta 

 argo serving for copulation (magnified about three diameters) ; 

 after KOELLIKER (Berichte der Zoot. Anstalt zu Wurzburg, 1849, 

 Tab. i. fig. 19); comp. pp. 821823. 



