282 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



To our great satisfaction we were also agreeably disappointed to find 

 that the specific gravity of the water in the pond remained steadily 

 abont the same as that found to prevail in the bay. The specific gravity 

 in the pond was 1.018, and 1.020 at times in the bay. to as low as 1.0175, 

 and the fluctuation of the specific gravity of the water in the pond was 

 found to be about the same as in the bay. 



At the head of the creek the specific gravity of the water was about 

 1.010. In this situation a good many oysters were living and growing; 

 but even this density is not so low as that prevalent in the waters of 

 Saint Jerome's Creek, where it fluctuates between 1.007 and 1.010, and 

 where excellent oysters are grown. 



From numerous observations and considerations based upon the facts 

 of distribution, it is believed that the oyster in all cases thrives best 

 in waters of a specific gravity about such as has been indicated above, 

 or from 1.007 to 1.020. 



Another equally important point to settle was whether a sufficient 

 amount of food would be generated in the pond to supply any young 

 or old oysters with nourishment. To our satisfaction we found im- 

 mediately after the diaphragm had been placed in the trench that 

 the confined waters of the pond acquired a distinctly brownish -green 

 tint, which we at first supposed was due to particles of dead, brown 

 organic matter. A microscopical investigation of the water showed 

 that in this we were in error, and that the brown color of the water was 

 largely due to the presence of innumerable microscopical plants, con- 

 sisting largely of diatoms, having brownish contents. It was also found 

 that immense multitudes of very small monads, with long flagella, 

 would collect upon floating chips and light objects at the surface of the 

 water during the warm mid-day hours. It seems, therefore, evident 

 that food was generated in abundance here, and greatly in excess of 

 what may be found in the open bay, and that one of the most impor- 

 tant conditions for the success of our experiment had been established. 



The final results fully confirmed this conclusion, inasmuch as we 

 found that spat grew just as rapidly in the pond as in the waters of the 

 open bay. There is, moreover, no reason to suppose that it would not 

 grow to a marketable size just as certainly as spat collected in the na- 

 tural way. 



COLLECTORS. 



The collectors used in our experiment were of the simplest possible 

 character, the object being to make the experiment as practical in 

 character as possible. To this end stakes were driven into the bottom 

 of the pond, extending above the surface some distance, to which oys- 

 ter shells, with holes punched through, were attached after being strung 

 upon galvanized iron wire. A number of these simple collectors were 

 placed in the pond, each set being marked with the date on which they 

 were placed in position, in order to afford data for a more detailed 

 study of the results of the experiment. 



