EFFECT OF ORGANIC SUBSTANCES ON OYSTERS 



183 



15 to 25 minutes and transferred to a 23-ml. 

 cuvette. The color density was measured and 

 recorded as —Log T. 



The densities thus determined were converted 

 to equivalent arabinose in milligrams-per-liter by 

 the use of a graph constructed from standard dilu- 

 tions of 1-arabinose. The general precautions 

 pertaining to colorimetry were observed through- 

 out. The data for a set of standards are pre- 

 sented in table A-l. The 1-arabinose was checked 

 for adsorption of atmospheric moisture by a series 

 of weighings made over a period of 20 minutes at 

 5-minute intervals. No increase in weight was 

 detectable on the analytical balance. 



Table A-l. — {—Log 7 1 ) values for various concentrations 

 of l-arabinose 



MEASURING OYSTER ACTIVITY 



The principle of the rubber apron originated by 

 Moore (1908), and the constant-level chamber 

 developed by Galtsoff (1926) were combined in 

 this study to improve the accuracy of measure- 

 ments of the pumping rate of oysters reported by 

 Nelson (1936). 



We found the attachment of the dental dam to 

 the valves of the oyster was done most expediently 

 with a small soldering nail and sticks of beeswax. 

 The soldering nail was connected to a suitable 

 rheostat and the voltage set to keep the soldering 

 nail just at, or slightly over, the melting tempera- 

 ture of the beeswax. The beeswax was worked 

 into small pencils and applied to the shell of the 

 oyster with the point of the soldering nail. First, 

 the wax was applied along the line of attachment 

 of the rubber to fill the irregularities of the shell 

 which could cause leaks. After this, a small wall 

 of wax was built up and the rubber sealed to it. 

 At the hinges and in the region of the palliobrachial 



fusion, small pads of pyrex wool (instead of cotton) 

 were used as packing between the rubber mem- 

 brane and the shell. The glass does not lose its 

 resilience when wet, neither is it subject to 

 organic decay on long exposure to experimental 

 conditions. The oysters were held in position on 

 Hopkin's stands (fig. A-l) and connected to the 

 trough. To determine the amount of effluent, we 

 used a simple box with an automatic siphon in the 

 place of the usual dumping bucket (Collier and 

 Ray 1948). 



We acknowledge the great assistance of Drs. 

 W. E. Hanson and J. G. Erdman of the Mellon 

 Institute of Industrial Research, and we are 

 grateful to W. K. Bowman, of the Gulf Research 

 and Development Company, for providing us with 

 excellent electric kymographs built to the specifi- 

 cations of our project. Some of the early records 

 were made with a paper speed of 2 inches an hour, 

 but this was later changed to 4 inches an hour. 

 At the latter speed, we obtained 2 weeks of unin- 

 terrupted recording with superior amplification 

 of detail. 



DESCRIPTION OF SAMPLING DEVICE 



The sampling device (fig. A-2) consisted of a 

 wheel (A) whose circumference revolved under a 

 continuous stream of water (B), and thus caused 

 the equally spaced tubes (C) to be filled. The in- 

 terval of filling was regulated by the spacing of 

 the tubes and the velocity of the wheel. The 

 wheel was driven by a synchronous motor (D) 

 whose velocity was 1 revolution in 24 hours. 



The wheel was fastened to a vertical shaft by 

 means of a flange; the shaft was suspended at (E) 

 by means of a thrust bearing and set collar, and 

 was connected to the drive shaft of the motor 

 by a tubular coupling. In this manner, exposure 

 of the motor and bearing suspension to salt water 

 was minimized. 



The waste water overflowed onto absorbent 

 material, and this, in combination with the tight 

 lid, kept the atmosphere within the chamber 

 saturated. Evaporation was not sufficient to 

 affect the accuracy required (±0.05% o ) for salinity 

 determinations. 



The apparatus as used by us gave a 1 5-minute 

 composite sample every 1 or every 2 hours, as 

 desired. 



