2l8 



How to obtain it. 



They are often found in canals and similar habitats; they are 

 abundant in the Midlands, but several attempts that have been 

 made to introduce them into more northern waters have proved 

 abortive. 



Fig 38. Anadonta cygnea. 



On the bottoms of ponds and streams we should certainly 

 cultivate the bivalves, or Conchifera. The largest are the swan 

 mussel (Anadonta cygnea) and its varieties. They attain a length 

 of about six inches, and are not of a high food value when mature, 

 but when young they are eaten with avidity by many fishes. In 

 their infancy they are parasitic on fish, but their attacks do not 



Fig. 39. llnio inargaritifer. 



appear to be at all hurtful beyond slightly impeding the progress 

 of the fish to which they are attached in their movements through 

 the water. 



The Unionidos are similar bivalves, not quite so large as the 



