14 



very rudimentary in tlie oyster. When oysters are 

 removed from salt water to that which is less salt, a 

 similar enlargement of the animal takes place, which 

 may be entirely attributed to the effect of the action of 

 the well-known laws of osmosis, and should not be re- 

 garded as a fattening process at all, since the real "fat" 

 of the oyster is something vastly more substantial than 

 water, as will be learned in the sequel. Prof. P. Frazer, 

 Jr.,"^ has discussed the subject of fattening oysters by 

 means of osmosis. 



For my own part I believe that the turgid, translucent 

 appearance of the edges of the mantle in the oyster is 

 due to the passage inwards of water through the mouths 

 of numerous vessels Avhich ojpen freely on its surface ; 

 these from my microscopic examinations seemed to be 

 the extremities of the capillaries of the mantle, and I 

 find that for this belief 1 have the concurrent testimony 

 of other writers, (Bronn ; Klass. u. Ord. Ill, 384.) 



The nervous system of the oyster is very simple, being 

 composed of a pair of ganglia or masses of nervous mat- 

 ter, which lie just over the gullet, and from which a pair 

 of nerve cords pass backwards, one on each side, to join 

 the hinder pair which lie just beneath the adductor 

 muscle. The mantle receives nerve branches from the 

 hindmost ganglia, and these control the contraction and 

 elongation of the radiating bundles of muscular fibers as 

 well as those which lie length Avise along the margin ; the 

 former contract and withdraw the edges of the mantle 

 from the margin of the shell, while the latter in con- 

 tracting tend to crimp or fold its edges. The tentacles, 

 or organs of touch, are also mainly supplied from the 

 hindmost ganglia, while the internal organs are inner- 

 vated from the head ganglia. 



*0n Dialysis in Oyster Culture. Proc. Acad. Nat. Sciences, 27. 1875, pp. 442 — 43. 



