The habit of the sea mussel is to lie with the beak buried in the sand, or mud, and with the syphon end, 

 through which the food current enters, projecting into the water Eibove. The waving cilia attached to the gills 

 of the mussel cause a continual circulation of the water, sifting from it the microscopic organisms on which 

 the mussel feeds 



4t. ^m 



mirk)(M,^y)\ 



When the community is overcrowded, it is necessary for the mussels to stand on their heads to prevent the 

 individual food-bearing currents from being cut off, but there is usually no lack of food even under the most 

 •crowded conditions, for the minute water plants which form the staple supply increase so rapidly that, 

 unreduced, they would fill the ocean solid in less than a week 



359 



