DEMINERALIZATION MECHANISM OF BORING GASTROPODS 79 



enamel surfaces of permanent tooth crowns and on the polislied 

 surfaces of ground sections of enamel and dentin. The mineral in 

 tooth substance is calcium phosphate in the form of hydroxyapatite. 

 It was found that both enamel (Figs. 44 to 47) and dentin (Figs. 

 48 and 49) were damaged bv the glandular secretion. The rate of 

 attack was somewhat slower than in the case of the shells, and it was 

 necessary to prolong the treatment times to 60 to 100 hours by suc- 

 cessive application of freshly excised ABOs at approximately 24-hour 

 intervals. Although there is a small amount of carbonate (about 3 

 per cent) in tooth mineral, it seems unlikelv that the degree and 

 pattern of damage observed could be accounted for on the basis of 

 carbonate solubility alone. These results suggest that the ABO secre- 

 tion is probablv not specific for calcium carbonate, but that at least 

 calcium phosphate may also be attacked. 



Discussion and Conclusions 



Secretory activity of the accessorv boring organ of drilling gastro- 

 pods results primarily in a demineralization of the shell of prey, in 

 the course of which mineral crystals appear to be partially dissolved 

 and loosened. Dissolution of individual crvstals appears to proceed 

 irregularly, resulting not onlv in conspicuous intercrystalline spaces, 

 but also in serrated edges and shallow to deep pits. Whether this 

 differential rate of solution is due to the heterogeneous composition 

 of each crvstal, resulting in portions which are more vulnerable than 

 others, or to an uneven distribution of the chemical agent, is not 

 known. The former is more likelv in view of the fact that HCl and 

 versene produce grosslv similar effects on these crystals. The degree 



Figs. 26 to 31. Electron micrographs showing the character of the under- 

 lying nacreous surface following treatment with various chemical agents and 

 removal of debris by preliminary replication. ( X 6000.) 



.Fig. 26. Crassostrea virginica, 5 seconds in 0.1 n HCl, pH 1.0. 



Fig. 27. Murex fuhesccns, 5 seconds in 0.1 n HCl, pH 1.0. 



Fig. 28. C. virginica, 48 hours in 10 per cent versene, pH 8.0. 



Fig. 29. M. fulvescens, 24 hours in 10 per cent versene, pH 8.0. 



Fig. 30. M. fulvescens, 3 hours in ethylenediamine at 80°C. 



Fig. 31. C. virginica, 2 hours in boiling 60 per cent KOH. 



