OYSTER BOTTOMS IN MATAGORDA BAY. 75 



is evidence to show that a food value of 250,000 units will in a mod- 

 erate current produce fat oysters on a moderately dense bed, while 

 850,000 units will have a similar effect upon a very dense bed, like 

 Boggy Lump, exposed to currents of less velocity. The production of 

 oyster food in Matagorda Bay, therefore, can be considered on the 

 whole very satisfactory, and sufficient to support a vastly greater 

 oyster population than now exists. Taking into consideration not 

 only the immediate abundance of diatoms, etc., but the size of the 

 area over which they are distributed, the most favorable location for 

 oyster planting, so far as available food is concerned, lies in the 

 middle and on the peninsula side of the bay from just above Forked 

 Bayou Reef to the extreme lower limit of the survey, a large extent 

 of extremely productive water. 



METHODS EMPLOYED IN DETERMINING FOOD VALUE OF WATER. 



In the investigations of the oyster food of the waters of Matagorda 

 Bay the methods pursued were as follows : The water specimens, one 

 liter each, were taken by the survey party wherever density observa- 

 tions were made, at average intervals of about 1 mile, and, inclosed 

 in tightly corked bottles, were carried back to headquarters at the end 

 of the day and filtered. The filters are agate Avare or copper fun- 

 nels of 1 liter capacity, the small end being closed by a perforated 

 cork, over which is stretched a piece of fine bolting cloth supporting 

 a one-half inch stratum of well washed and sifted sand, fine enough 

 to pass through no. 11 bolting cloth, but too coarse to go through 

 no. 1. As the water in the funnels falls the walls are washed from 

 time to time with filtered water from a wash bottle or a pipette, so 

 that practically no diatoms or other organisms will adhere, and when 

 the specimen has entirely filtered the walls are given a final rinsing, 

 the cork is removed, and the sand washed with a small quantity of 

 water into a vial or small beaker. The precipitate is then energet- 

 ically shaken and the liquid immediately decanted off into a gradu- 

 ated vial, a small quantity of water is again added to the sand, and the 

 process repeated. As the sand is much coarser and heavier, it at 

 once settles, while the organisms are carried off by the successive 

 washings and collected in the vial, sufficient water then being added, 

 or abstracted after settling, to bring it to a standard measurement of 

 10 c. c. A few drops of formalin will preserve the organic contents 

 of the precipitates, which are kept in vials appropriately labeled 

 until such time as they can be examined. This method of filtration 

 is more rapid than that of precipitation usually employed, and, more- 

 over, the latter can be used only with difficulty on a rolling ship. 

 Comparative tests show that they give approximately equivalent re- 

 sults. One cubic centimeter of the precipitate is then transferred to a 

 Rafter cell and the diatoms in ten fields each 1 mm. square are iden- 



