NATURAL HISTORY OF THE MUSSEL 53 



that those attached to the land or sheltered side 

 of boulders are much larger and fuller than those 

 which are exposed to the force of the waves. 



If, on the other hand, the spat has settled on 

 the rich flats of some suitable estuary, we find that 

 there is a much more uniform growth, and that 

 compared with those grown for the same length 

 of time on the rocks of an exposed shore, the 

 average rate of growth has been much more rapid. 

 The difference is due to the additional amount of 

 suitable feeding brought into the estuary by the 

 fresh water, and to the shelter from storms. 



Another factor, however, which greatly in- 

 fluences the growth of a vast number of mussels, 

 is overcrowding. If we take into consideration 

 the enormous number of young which a single 

 pair of mussels may produce (probably between 

 two and three million) it is no matter for astonish- 

 ment that a considerable proportion of that 

 number should be annihilated, through want of 

 space for healthy growth. If a cluster of mussels 

 growing in a natural condition be examined, the 

 large ones will be found to be much less numer- 

 ous than the minute individuals which, in closely 

 packed array, entirely fill up the interstices around 

 the shells of the large and specially favoured few. 



