DEMINERALIZATION MECHANISM OF BORING GASTROPODS 63 



ceps. The snail was then cut in two at the base of the tentacles with 

 scissors, thus separating the visceral from the pedal mass. The foot 

 was pinned upside down to an eraser embedded in a wax-filled bowl, 

 exposing the ABO pore. The ABO, including its short stalk, was ex- 

 cised with iris scissors and watchmaker's forceps under a binocular 

 magnification of 10 times. In Eupleuia, the ABO was usually everted 

 by pressure of pinning and was readily removed, but in Urosalpinx 

 the organ had to be cut out of its pedal sac (Carriker, 1943, Fig. 

 10 ) . The operation was performed out of sea water to minimize the 

 dilution of ABO secretion. The average diameter of relaxed ABOs 

 used in these experiments in U. c. folh/ensis ranged from 1.8 to 2.6 

 mm, and in E. c. etterae from 1.5 to 2.0 mm. Because of the relatively 

 small size of the organs and danger of rapid desiccation in air, they 

 were transferred immediately from the snail to the substrates with 

 fine forceps. 



ABO-Substrate Preparations 



The simplest preparation consisted of the excised ABO placed in 

 a drop of filtered sea water (Millipore filter, pore size 1.2 microns) 

 2 to 3 times its diameter on an area of the calcareous substrate 

 marked with lead pencil to facilitate subsequent localization of the 

 site of the etching. 



A deeper and more precisely circumscribed etching was often ob- 

 tained by use of an artificial chamber, and the life of the excised 

 ABO was extended by the use of antibiotics. We employed Millipore- 

 filtered sea water containing 100 units of mycostatin and 250 [xg of 

 Chloromycetin per ml. After being dipped in this solution the ABO 

 was inserted in a short section of Intramedic polyethylene tubing 

 with disk down and in contact with the substrate. This manipulation 

 was performed under a magnification of 10 times with fine forceps. 

 The diameter of tubing selected permitted the ABO to be housed 

 snugly and the disk of the ABO to be supported squarely on the 

 substrate. The latter was requisite since maximum etching was ob- 

 tained directly under the ABO when the gland was in direct contact 

 with the substrate. Additional sea water-antibiotics solution was 

 added to provide a narrow zone of fluid around the outside of the 

 chamber at the tube-substrate interface. Drops of the sea water- 



