NATURAL HISTORY OF THE MUSSEL 59 



thicken the shell, an extreme of fresh water 

 weakens the animal and impoverishes its shell. 

 In either case the best bait mussel cannot be 

 produced. 



Scalps, to grow mussels rapidly and well, must 

 not be long tmcovered by the tide. On a shelving 

 beach this can often be seen most clearly at low 

 water, large mussels being found near the water 

 and a gradually diminishing series extending up 

 the beach, the mussels being all of the same age. 

 An exactly similar condition can be observed in 

 the case of plantations of Scotch fir on a moun- 

 tain side, — a rich, full growth at the foot of the 

 slope, a struggling existence at the top. 



Beds therefore should be protected as far as 

 possible from the deposition of silt. This evil, if 

 present, can only be remedied by transplanting 

 the mussels from the high bed, and causing the 

 available currents to scour and wash down the 

 deposit. The mussels can then be replaced, or 

 fresh seed sown. To do this satisfactorily a 

 considerable area of mussel ground must be at 

 command. In many places scouring cannot be 

 satisfactorily accomplished because of the small 

 area at command. When it is quite evident that 

 beds are too high, a delay in transplanting, so as 



