excepting, near the outlet which becomes brackish at times, due 

 to ' ' backing up " of salt water. 



TowiNGS.- — As stated above, the swimming movements of 

 the oyster larvae are directed chiefly towards keeping it at the 

 surface of the water. At a depth of sixteen feet comparatively 

 few larvae are found, somewhat more during mid-day and after 

 a heavy rain, when the water density is several points less at 

 the surface than at a depth. But the difference is not so much 

 as might be expected. An average of fifty towings made imder 

 like conditions in approximately the same locality and at the 

 same speed and extending over a period of just thirty minutes, 

 showed approximately ninety-two thousand larvae caught in a 

 tow net seven inches in diameter. An average of forty towings, 

 sixteen of which were made simultaneously with the above, only 

 at a depth of 15 feet showed approximately 500 larvae at each 

 towing. While at a depth of 20 feet, 96 was the most counted 

 at any one time. The summary of the following towings taken at 

 about the same season, but in a different locality, showed these 

 results: the average of 54 towings at the surface about 108,000; 

 38 towings at depth of 10 feet about 5,000 ; 38 towings at a depth 

 of 15 feet about 800. The above is the record of towings made 

 at all hours varying from 4.00 a. m. to 11 :00 p. m., under all 

 conditions of weather, cloudy and clear, and in temperatures of 

 water varying from 18 degrees to 31 degrees Centegrade, 64° 

 to 88° Fahrenheit, and water density varying from 1.0150 to 

 1.0280 (corrected for temperature), there w^as a slight 

 decrease in numbers of larvae at a depth when tows were 

 made from 10 a. m. to 3 p. m. An average of 8 towings made 

 after heavy rains showed the following: At surface, 60,000, 

 at ten feet, 9,000 ; at fifteen feet, 2,000. 



At the end of two weeks, normally, the time varying accord- 

 ing to conditions of food and temperature, the oyster larvaa 

 either attaches itself to some solid object or settles to the bot- 

 tom. This is a critical time in the life of the oyster, and it 

 is at this age probably that more oysters perish than at any 

 other time. The free swimming larvae are the prey of, and go 

 to make up the food of millions of other animals. Such fishes 

 as the Menhaden, Mullet and others that get their food by 



