DEMINERALIZATION MECHANISM OF BORING GASTROPODS 77 



Morphological Characteristics of Mineral Calcite and 

 Aragonite Subjected to ABO Activity 



The next step in these experiments was to define more precisely 

 the properties of ABO secretion with regard to its capacity to attack 

 the organic and inorganic components o£ shell. In order to deter- 

 mine the effect of ABO activity on the inorganic portion alone, we 

 placed ABOs for 3 hours on flat cleaved smfaces of pme mineral 

 calcite and aragonite crystals, which obviously contained no organic 

 matrix. In such specimens definite surface alterations were observed 

 (Figs. 38 to 43), and these resembled in large degree the changes 

 which were earlier observed on shell (Figs. 16, 17, 12 to 15). Al- 

 though the crystalline structure of pure calcite and aragonite is ob- 

 viously different from that in mollusk shell, it is of interest that the 

 earliest surface changes in the calcite and aragonite took the form 

 of small pits (Fig. 40) which later coalesced to form much larger 

 depressions (Fig. 43). The fact was thus established that the ABO 

 secretion is capable of attacking the inorganic constituents of mollusk 

 shells. 



,A comparable series of studies is now in progress in which isolated 

 shell matrix is being subjected to similar activity. Considerable tech- 

 nical difficulty has been encountered and the work has not progressed 

 far enough at this point to warrant discussion of the results. 



Effect of the ABO Secretion on Mineralized Tissue 

 Containing Calcium Phosphate 



In order to characterize the ABO secretion further, we carried 

 out an experiment to determine whether its activity is specific for 

 calcium carbonate. Excised glands were placed on the polished outer 



Figs. 20 to 25. A group of electron micrographs made from pseudo replicas 

 on which thin layers of loosened crystalline material were removed from the 

 nacreous surfaces of shells subjected directly to the action of excised ABOs. 

 The pitted surfaces and serrated edges of the crystals are clearly shown. 

 (X6000.) 



Figs. 20 to 23. ABO of Urosalpinx cinerea follyensis on Crassostrca vir- 

 ginica. 



Figs. 24 and 25. ABO of Poliniccs duplicdfiis on Murex fuhcscens. 



