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



Whether the mechanism is common to all boring gastropods will 

 not be known until man)' more species around the world have been 

 investigated. 



Summary 



1. Studies of the demineralization-boring mechanism of drilling 

 naticid and muricid gastropods were continued. The following spe- 

 cies of boring snails were investigated: Urosalpinx cinerea follijensis, 

 Eupleura caudata etterae, Murex fulvescens, Murex brevifrons, 

 Polinices duplicatus, and Simim perspectivum. The following sub- 

 strates were utilized: shell (CaCOa as calcite) of the bivalves Cras- 

 sostrea virginica, Dosinia discus, and Spisula solidissima; shell 

 ( CaCOa as aragonite ) of the snail Murex fulvescens; human enamel 

 and dentin (calcium phosphate as hydroxyapatite ) ; and pure inor- 

 ganic calcite and aragonite (CaCO:i) without organic matrix. Bore 

 holes were made by living gastropods in the laboratory; and etch- 

 ings on substrates were produced by the secretion of the excised ac- 

 cessory boring organ (ABO) and ABO homogenates on special 

 ABO-substrate preparations. These etchings were studied by micro- 

 radiography and by optical and electron microscopy. 



2. Repeated pH determinations of the fluid on normal ABOs, ex- 

 cised ABOs, and ABO homogenates gave a neutral or slightly 

 alkaline reaction. The active agent of ABOs heated to 80 °C was 

 almost entirely inactivated. 



3. Activitv of the secretion of the ABO resulted primarily in a 

 demineralization of the shell of prey; in the course of this, mineral 

 crystals were partiallv dissolved and loosened for ready removal by 

 radular denticles. Action on the organic matrix is not yet known, 

 though it mav be less readilv attacked than the mineral constituents 

 of shell. Both inorganic calcite and aragonite were soluble in glandu- 

 lar secretion; but the secretion was not specific for CaCOs, as it 

 acted also on calcium phosphate. 



4. The action of the ABO secretion of different species of boring 

 gastropods tested to date appeared to be similar, not only on a given 

 species of mollusk shell, l^ut on the different species employed. 

 Variations in the ultrastructural topography of different etchings 



