146 



ANARTHROPODA 



FIG. 171. A freshwater mussel with the right valve mantle and gills and some 

 tissue at the base of the foot removed ; a, anterior adductor muscle ; au, auricle 

 of the heart ; ft, foot ; g, reproductive gland ; gl, gill ; i, intestine ; k, kidney ; 

 m, mantle ; n, nerve ganglia connected by nerve cords o ; p, posterior adductor ; 

 pi, labial palps ; si, siphon ; v, ventricle. The dark lines on the mantle and 

 foot are blood vessels. 



pose it is to cause the water to flow in and out through 

 the siphons, thereby bringing in food and oxygen. By 

 detaching a minute portion of the gill of a live mussel 

 and mounting it in a drop of water on a glass slip and 

 examining with the microscope the cilia (hairlike pro- 

 cesses) may be seen in motion. 



The heart, consisting of two auricles and a ventricle, is 

 seen by removing the dorsal portion of the mantle. In a 

 live mussel opened, the heart can be noticed beating, as 

 the milky blood passes from the auricles to the ventricle 

 and thence through the pedal artery to the foot and body. 

 It then goes to the gills where carbon dioxide is given off 

 and oxygen received before it is returned to the heart. 



