1308 BULLETIN OF THE BUREAU OF FISHERIES. 



appetite at the beginning of the experiment is provided by comparison of the 

 results obtained in the two lots fed for different periods. 



My first experiments were with bolting cloth aprons, but it was found diffi- 

 cult to keep them covered with sand, especially close to the edges of the dish, 

 and also to secure good adhesion between the shell and the apron. These 

 defects in some cases permitted the infiltration of fine mud and other extraneous 

 matter. Such difficulties have been obviated by the use of sheet-rubber 

 " aprons " as described. The latter have been in use for four or five months and 

 have proved satisfactory, but there has not been time for the tabulation of the 

 quantitative results. 



It is believed that the apparatus and methods of research above described 

 furnish for the first time efficient instruments for strictly quantitative studies 

 of the food and feeding of oysters and similar moUusca, and they also furnish 

 data for determining the amount of water filtered through the gills. In addition 

 to the scientific interest attaching to the studies it is believed that they will lay 

 the foundation for valuable economic data. As is well known to those who have 

 made a study of the oyster fisheries, much time and money is lost in futile 

 attempts to grow oysters in localities which eventually prove unsuitable. In 

 many cases these failures are due to a paucity of food, the oysters failing to 

 fatten. If there could be determined the minimum food unit requisite under 

 varying conditions of bottom, currents, and density of oyster population, the 

 waste of time, money, and effort in useless planting could be largely prevented. 



As a preliminary to the determination of such unit, it is necessary to deter- 

 mine with accuracy the relations existing between the oysters and the plants 

 which constitute their diet. We must know the exact relation existing between 

 the food consumed by oysters which are rapidly growing and fattening and by 

 those which are not. We must determine how much more food an oyster will 

 consume in strong currents than when living in sluggish waters equally rich per 

 unit of volume, and it will be necessary to learn also the water food content 

 required to supply the minimum requisite under varying conditions of current. 



The experiments already conducted have shown that all of these data can 

 be obtained with considerable accuracy by the means above described, and by 

 conducting further research in regions such as Lynnhaven Bay, where the 

 quantity of oysters on the bottom over considerable areas can be approximately 

 arrived at, they can be given concrete application. The formulation of the 

 desired unit will require much patient research and observation, the study of 

 currents, of the behavior of oysters under various natural conditions, and pos- 

 sibly of the reproductive activity of diatoms and other food organisms, but it is 

 believed that we are now in possession of instruments which warrant an attempt 

 at the solution of the problem. 



