MOLLUSKS. 



329 



of these animals, I will give you the anatomy of one of 

 them in Fig. 261. One of the valves is removed. You 



I ll 



.II 4 



/Anterior 

 \Ganglia. 



Mantle. 



Respiratory Tubes. 

 Fig. 261. Anatomy of an Acephalous Mollusk. 



see the mantle, fringed all around its edge. This lines 

 the whole shell, and covers the animal. It is its skin. 

 You see the two muscles that, by their contraction, bring 

 the valves together, and the fleshy foot, which can be 

 made to protrude when the valves are left to go apart by 

 the action of the elastic ligament. This foot, which is 



