4 -THE FOOD OF THE OYSTER, CLAM, AND RIBBED MUSSEL. 



By John P. Lotsy, Ph. D. 



. During a stay on the James River, Virginia, in the summer of 1892, 

 I had hoped to study the food supply of both the young (embryonic) 

 and the adult oyster, but as the season was too far advanced to allow 

 the collection of any embryos only the latter i)art of the investigation 

 proved feasible. 



Collections Avere made at many places on both sides of the James 

 River from Newport News to Old Point Comfort, specimens being- 

 obtained from both natural and cultivated beds, from muddy and 

 sandy bottom, and from piles and stones, especially around Fort Wool 

 on the Ripraps. They were taken from various depths, some being 

 gathered on a bottom left exposed at low tide; others were obtained 

 which did not grow on the bottom, but which were, so to speak, sus- 

 pended in the water near the surface, attached to piles and rocks, also 

 exposed during low tide; still others were collected from deeper places, 

 never uncovered by the tide, growing either on the bottom or on per- 

 manently submerged stones and piles. To determine whether any 

 changes in the food supply were dependent upon the season of the year, 

 material was obtained daily from the beginning of June until the end 

 of September, and whenever an opportunity offered shipments brought 

 from farther up the river were examined to see if the greater amount 

 of fresh water there present had any iniluence on the character of 

 their food. 



Before entering further into details it is necessary to note that the 

 oyster is constantly ingesting a stream of water, which, passing the 

 mouth, brings near and into this always opened organ all the objects of 

 greater or less size coming within the influence of this stream. The 

 mere presence, therefore, of particles of various organic matter in its 

 stomach, even in great quantities, does not indicate that the oyster 

 uses them as food, but only proves that these particles were present in 

 the surrounding water at the time of ingestion. This is a consider- 

 ation too often overlooked. If an animal of the structure of an oyster 

 be idaced in a bucket of water in which is suspended a great number 

 of carmine granules, these granules will doubtless be found in the 

 stomach of the animal after a certain length of time, yet nobody would 

 claim that they were the food of the oyster. A similar thing occurs in 

 nature. In the many oysters which I have opened and of which I 

 iuvestigated the stomach contents 1 never failed to find numerous 



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