THE OYSTER. 53 



are to be seen deep muscular cayities, occupying the 

 place of the heart {h), and sending their moisture to the 

 small skin through which they come in contact with 

 the water or the air. 



In his '' Outline of the Animal Kingdom," Professor 

 Rymer Jones most happily describes all these peculiari- 

 ties. ''Wonderful indeed is the elaborate mechanism," 

 are his words, '' employed to effect the double purpose 

 of renewing the respired fluid and feeding the helpless 

 inhabitants of these shells ! Every filament of the bran- 

 chial fringe, examined under a powerful microscope, is 

 found to be covered with countless cilia in constant 

 vibration, causing, by their united efforts, powerful and 

 rapid currents, which, sweeping over the surface of the 

 gills, hurry towards the mouth whatever floating animal- 

 cules, or nutritious particles, may be brought within the' 

 limits of their action, and thus bring streams of nutritive 

 molecules to the very aperture through which they are 

 conveyed to the stomach, the lips and labial fringes act- 

 ing as sentinels to admit or refuse entrance, as the matter 

 may be of a wholesome or pernicious character." 



^Nature, too, has given the oyster a sensitive percep- 

 tion of the changes of light as the means of its protec- 

 tion from the many enemies it has to contend with ; for 

 if the shadow of an approaching boat is thrown forward 

 so as to cover it, it closes the valves of its shell before 

 any undulation of the water can have reached it. This 

 sensitiveness is easily studied in the marine vivary, 

 where the oyster, with its beautiful cilia, more beautiful 

 by far than the richest lace of a bride's wedding di'ess, 

 is always an object of great interest. 



