THE STRUCTURE OF THE OYSTER. 8 1 



observed. As a breathing organ it is perfect ; and as an 

 organ for securing food it is surely unrivalled for the 

 exquisite beauty of its structure. (/") 



To adopt the eloquent words of Professor T. R. Jones, 

 (g) "Wonderful, indeed, is the elaborate mechanism 

 employed to effect the double purpose of renewing the 

 respired fluid, and feeding the helpless inhabitants of these 

 shells ! Every filament of the branchial 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 entire surface of the gills, hurry towards the 

 mouth whatever floating animalcules 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 acting as sentinels to admit or refuse 

 entrance, as the matter supplied may be of a wholesome 

 or pernicious character. So energetic is the ciliary move- 

 ment over the entire extent of the branchial organs, that 

 if any portion of the gills be cut off with scissors it imme- 

 diately swims away, and continues to row itself in a given 

 direction as long as the cilia on its surface continue their 



movements.' 



Nor should we omit to observe that several transparent 

 arborescing blood vessels are placed between the outer 

 membrane and the substances of the body, and on the lips 

 of the oyster, which are visible to the unaided eye, from 

 their continuity with the opaque fat. As all the impres- 

 sions made on the oyster are those of immediate contact, 

 every part of its exterior surface appears highly sensitive. 



(/) " Annals of Natural History," vol. 8, pp. 375, 376. 

 (g) " Animal Kingdom." 



