FRESH-WATER MUSSEL 



377 



Oxygen is absorbed by the capillaries and carbon dioxide passed 

 into the water where it is discharged to the outside through the 

 dorsal siphon. 



Circulation 



The heart which is composed of a ventricle and two auricles lies 

 in the pericardium. The ventricle, a muscular organ, surrounds 

 the rectum and drives blood forward through the anterior aorta 

 and backward through the posterior aorta. Both aortae give off 

 arteries which ramify all parts of the body. Most of the returning 

 blood is carried to the kidneys by means of the vena caval vein. 

 Within the latter, nitrogenous wastes are removed, and the blood 

 then flows to the gills through afferent branchial veins; after puri- 

 fication in the gills it is returned to the auricles by way of the 

 efferent branchial veins. The blood is colorless and contains several 

 types of white corpuscles. 



Nervous System and Sense Organs 



Situated on each side of the esophagus is a cerebropleural gan- 

 glion, the two ganglia being connected by means of a cerebral com- 

 missure which passes above the esophagus. Each ganglion gives 



Vertical ^'^^^- oddacbor M 

 water tubes \ Hidnoy 



Exholant 

 Siphon 



Arjus 



Pericardial wall Reno -pericardial pore 



Post, aorta ! Ventricle j Excretory pore 



Auricle I | Ant.aorta Liver 



I ! 1 Stomach \ cerebral 

 I I j I ; commissure 



I I 

 I ' 



i; 



Ant. adductor 

 muscle 



Inhalant 

 siphon 



Visceral Q. Qonod \ } root '. ^°"^^ 



Intestine Pedal Q. Cerebro pleural &, 



Fig. 145. — Internal anatomy of Lampsilis anodontoides. 



