Ciliary Mechanisms 63 



have to be accomplished directly against the incurrent 

 stream of. water. The palps function, as in Venus, in 

 disposing of material that they receive from the gills. 



There is a widespread belief that oysters and clams 

 may be fattened with such substances as corn-meal. 

 Even those well acquainted with the subject often have 

 supposed that bivalves had the power of taking such ma- 

 terial into the mouth. The following is a statement 

 on the subject published in an authoritative and valuable 

 guide to oyster culture : — 



" Experiments have been made with a view to feeding 

 the adult oysters upon corn-meal or some similar sub- 

 stance, but such attempts have been of no practical 

 value. There is no doubt that they would eat corn- 

 meal or any other substance in a sufficiently fine state 

 of division to be acted upon by the cilia. The oyster 

 is incapable of making a selection of its food, and prob- 

 ably any substance, nutritious, inert, or injurious, would 

 be swept into the mouth with complete indifference ex- 

 cept as to the result. Corn-meal and similar substances 

 would doubtless be nutritious, but their use must be so 

 wasteful that the value of the meal would be greater 

 than that of the oyster produced." 



In view of the account of the feeding habits of 

 bivalves here given, these statements require some inter- 

 pretation. Corn-meal ground to microscopically small 

 particles might be taken into the mouth of oyster or clam 

 if brought to the gill surfaces a very little at a time, but 

 even in a laboratory experiment, it would not be easy to 

 arrange these conditions properly. In such experiments 

 as those to which the writer of the quoted paragraph 

 refers, in which corn-meal, as ordinarily ground, is 

 merely thrown into the water over the bivalves, or even 



