1896.] NATURAL SCIENCES OF PHILADELPHIA. 279 



let the average weight or bulk of diatoms for each cubic metre of 

 such a region be determined and used as a standard of comparison, 

 by means of which the culturist may estimate the value of neigh- 

 boring waters. 



Corporations such as are now rapidly securing control of the best 

 oyster grounds of the coast, will not long be content to work under 

 the rule-of-thumb methods of the unscientific oysterman. The ex- 

 periments of laying out extensive oyster beds, or establishing fatten- 

 ing parks, are too costly to be undertaken on the basis of guess-work 

 as to whether conditions are or are not favorable. The money in- 

 vested in an oyster bed of one hundred thousand bushels is so great 

 that a year's difference in the time required by the plants to reach 

 marketable size means a very considerable profit or loss to the 

 planters. 



How to turn over the investment every two or three years, in- 

 stead of every five years, is a question which affects very materially 

 the dividends of a corporation engaged in oyster culture. In cer- 

 tain regions, the oysters grow rapidly in size, but do not become 

 sufficiently fat to command the prices paid for oysters of a similar 

 size from other beds. These thin oysters, for a few cents a bushel, 

 can be transferred to parks or fattening ponds, where, by supplying 

 them with waters rich in diatoms, they will become " primes " in 

 the course of a few weeks. 



The advantage of such fattening is obvious, as is the fact that the 

 time consumed in the process is a most important factor, the jii'ofit 

 depending on whether the parks can be emptied of oysters and re- 

 filled every three weeks or every six weeks. To regulate conditions 

 of this kind it is not enough to wait for results, to judge from day 

 to day whether the oysters are fattening or not, and to judge the 

 quality of the water of the park by the effects seen on the oysters. This 

 method is unprofitable ; it is either too slow, too uncertain or too 

 wasteful. Variation in rainfall, in temperature, etc., Avill affect the 

 relative number of food organisms in the water so materially that 

 the best results can be secured only by a daily test of the supply. 



Water rich in diatoms is too precious to be allowed to pass 

 through the parks in quantities larger than necessary to bring the 

 oysters to perfection in the shortest possible time. How now shall 

 the ostreaculturist ascertain quickly and accurately the amount of 

 plankton in the water of his parks and claires from day to day, or 

 decide upon the best places for the location of new beds as regards 

 food supply? 



