64 M. R. CARRIKER, D. B. SCOTT, AND G. N. MARTIN, JR. 



antibiotics solution (pH 6.8) placed on shell as a control produced 

 no disfigurement. Interposition of glass wool fibers between the 

 ABO and the substrate produced a more diffuse pattern of dissolu- 

 tion. Application of the entire pedal region with everted ABO did 

 not increase the degree of etching over that produced by excised 

 ABO alone. ABO-substrate preparations were housed at room tem- 

 perature in a covered glass or plastic chamber on wet cheesecloth 

 to prevent drying. After an interval of 3 to 24 hours the ABO-cham- 

 ber preparation was flushed from the substrate by a stream of dis- 

 tilled water, the substrate surface was air dried to prevent scratching, 

 and the substrate was stored in dustproof containers. The time when 

 the activity of the ABO ceases after excision is not known. At high 

 summer temperatures the ABO starts to disintegrate after about 20 

 hours, but with the use of antibiotics the organ retains its form for 

 a much longer period, and thus the pattern of etching can be related 

 preciselv to its creases and peripheral contour. 



pH Determinations 



Minute strips of short-range pH indicator papers, the color veri- 

 fied against standardized buffer solutions checked with a pH meter, 

 were applied to specimens and compared with the color standards 

 under the microscope. 



ABO Homogenates 



ABOs from 25 U. c. folhjensis were excised rapidly, placed in two 

 drops of sea water-antibiotics in an iced vessel, finely homogenized 

 by grinding with fine sand, and diluted to a final volume 10 and 50 

 times that of the ABOs with the same sea water-antibiotics solution. 



Artificial Etchings 



These were produced by application of various chemical agents 

 to portions of the valves of C. virginica and M. fiilvescens. Shell 

 surfaces were immersed for periods varying from 5 to 60 seconds in 

 0.1 N HCl (pH 1.0), 0.1 N lactic acid (pH adjusted to 5.0 with 

 NaOH); for 2 minutes to 3 hours in boiling 60 per cent KOH; for 

 1 to 3 hours in 80 per cent ethylenediamine at 80°C; and for 24 and 



