180 THE FRESH-WATER MUSSEL [CH. VI 



rating tissue and foreign bodies which have entered the 

 system. The plasma contains large quantities of cal- 

 careous salts in solution. The respiratory interchange of 

 gases, though primarily taking place in the gills and 



12 



10 - 



-G 



Fig. 33. A. Diagrammatic section through Anodonta to show the 

 circulation of the blood. B. Section through Anodonta near the 

 posterior edge of the foot. From Howes. 



A. 1. Right auricle. 2. Ventricle. 3. Keber's organ. 4. Vena 

 cava. 5. Efferent branchial trunk. 6. Efferent pallial vessel. 

 7. Efferent branchial vessel. 8. Branchiae. 9. Afferent 

 branchial vessel. 10. Efferent renal vessel. 11. Afferent 

 branchial trunk. 12. Afferent renal vessel. 13. Rectum. 



B. 1. Right auricle. 2. Epibranchial chamber. 3. Ventricle. 

 4. Vena cava. 5. Non-glandular part of the kidney. 6. Glandular 

 part of the kidney. 7. Intestine in foot. 8. Pericardium. 

 9. Shell. 10. Ligament of shell. 



mantle, is also very largely effected by the surface of the 

 foot, especially when this is distended, and by that of the 

 visceral region of the body. 



