Grave (8) on the oyster are of great interest. By a senes of 

 careful experiments he determined that oysters that had been 

 kept out of water and in filtered water until most of the food 

 had been digested or passed through the alimentary canal col- 

 lected on an average, upon being returned to the bottom from 

 which they were taken, " 385 diatoms during the first hour, 550 

 during the second, 1,406 during the third and 4,301 during the 

 fourth. This increasing rate of feeding is probably due to the 

 gradual recovery on the part of the oysters from the shock of 

 their unusual treatment in the laboratory. The rate at which 

 feeding took place during the fourth hour is probably nearer the 

 rate at which it occurs with oysters living undisturbed on the 



beds." 



■ From these and other observations Grave draws conclusions 

 regarding the length of time that an oyster must feed and the 

 amount of food that water must contain, in order that oysters 

 shall get proper food supply, that are open to criticism. He 

 says, " The work on the food resources of Newport river show 

 the average number of diatoms per liter (or about a quart) 

 available to oysters on the natural beds, during the summers of 

 1900, 1901 and 1902 to be 23,432, and that the oysters of salable 

 size examined during this time contained, on an average, 11,453 

 diatoms. If the usual rate of feeding under natural conditions 

 is near the figure obtained from the above experiment, 4,301 

 diatoms per hour, then three hours is ample feeding time for an 

 03-ster; and taking 23,432 as the average amount of food con- 

 tained in a liter of water over the natural oyster ground, it 

 follows that in collecting its daily meal (11,453 diatoms) an 

 oyster must filter altogether about 500 cc, or 16 oz. of water, 

 and that about 167 cc, or sVs oz., are filtered per hour." The 

 error is in taking 11,453 diatoms, the average number to be 

 found in an oyster's stomach at one time, as the average daily 

 meal. This does not take into account the rate of digestion and 

 accordingly the number that actually pass into the alimentary 

 canal in a day is an unknown quantity. The observations indi- 

 cate, however, that the number of diatoms used by an oyster is 

 enormous and that the part taken by lamellibranchs in convert- 

 ing this great wealth of food material into a form that is avail- 

 able for the higher animals is very considerable. (See 

 Brooks, 3.) 



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