THE MUSSEL. 67 



PLATE XVI. 



THE MUSSEL. ORGANS OP CIRCULATION. THE NERVOUS SYSTEM. THE EMBRYO, ETC. 



FIG. I. The arterial system, seen from the right side, after injection from the ventricle. 



With the exception of a small anterior portion marked *, the right pallial lobe has heen 

 removed, and with it the gills of that side. The pericardium was opened up, and the 

 mesosoma removed to the level of the alimentary canal. Nat. size. 



FIG. II. The efferent pallial, efferent branchial and related vessels, seen from the 

 left side after injection from the auricle. 



The efferent branchial trunks are drawn, as seen after removal of the mantle, and no 

 note is taken of the extensive system of pallial sinuses connected with the trunk, br.e'. 

 Nat. size. 



FIG. III. Dissection from the right side, to show the great veins in relation to 

 the excretory organ. 



The mantle lobe was removed, and the external gill lamina opened up. 



The afferent branchial trunk and its branches, and the so-called vena cava were injected 

 direct, after removal of the right auricle. 



For further details see Langer (71). 



Fleming (64) records some observations upon the blood corpuscles and lacunae of this 

 animal, together with an ingenious method of injection. Nat. size. 



FIG. IV. Slightly diagrammatic representation of a transverse section across the 

 middle pericardial region, after injection, x 1|. 



The channels shaded lightly, with the exception of that adjacent to the letter/., are 

 those carrying the aerated blood, x 11. 



FIG. V. Transverse section across A. of Fig. VI. of Plate XV., seen from the front, 

 to show the relations of the adductor muscle to the valves, and of the labial palps to the mouth. 



FIG. VI. Transverse section across B. of the same, the excretory and genital ducts 

 having been opened up on the left side. 



FIG. VII. Transverse section across C. of the same, passing through the auriculo- 

 ventricular valves and the great aperture of communication between the supra and infra- 

 branchial chambers. 



FIG. VIII. Transverse section across D. of the same. 



