60 M. R. CAERIKER, D. B. SCOTT, AND G. N. MARTIN, JR. 



ings in a few minutes to several hours. These ranged from faint 

 markings to definite shallow indentations in the shell, and they 

 assumed the diameter and form of the distal disk of the organ. The 

 secretion altered the gloss of the shell, leaving a conspicuously 

 roughened surface. 



The secretion of the ABO has not yet been characterized. In- 

 vestigations by Ankel (1938), Fischer (1922), and Hirsch (1915) 

 in which fluids from the organ and from incomplete perforations 

 were tested with pH indicator papers, and fluids from homogenates 

 of the organ were titrated with NaOH, indicated a neutral reaction. 



The fact that acids have not yet been identified in the secretion 

 of the ABO of either Muricidae or Naticidae, the suggestion of 

 Hirsch (1915) that a calcase may be present in the secretion, and 

 the experimental use of chelating agents for demineralization ( Galts- 

 off, 1955; Gregoire, 1957) have prompted the hypotheses that in the 

 chemical phase of boring the glandular epithelium of the ABO may 

 secrete a conchiolinase which might act upon the matrix of shell, 

 or a calcase and or a chelating agent which might solubilize the 

 mineral component, or both. ( See Wilbur, 1960, for a discussion of 

 the structure of mollusk shell. ) Since boring also involves mechanical 

 rasping, chemical agents need not completely destroy the shell pre- 

 paratory to remo\ al bv radulae. Weakening of either the organic or 

 the mineral components would permit removal of shell material by 

 radular denticles. 



Since 1960 we have been conducting a joint studv of the effect of 

 the ABO secretion of muricid and naticid snails on calcareous sub- 

 strates in an effort to provide a preliminary characterization of this 

 secretion and to contribute further information on the demineraliza- 

 tion-boring mechanism. These investigations have included prin- 

 cipally microradiography of sections of bore holes; physiological, 

 optical, and electron microscopic study of the action of the excised 

 ABOs and ABO homogenates on a variety of calcareous substrates; 

 and a comparison of these effects with the action of several artificial 

 agents on the same substrates. The present paper reports progress 

 made in these studies. Comparative morphological, cvtological, cy- 

 tochemical, and ultrastructural investigations of the ABO itself are 



