LIST OF ILLUSTRATIONS 



FIG. PAGE 



1. Valve of Ceylon pearl oyster 19 



2. Section (diagrammatic) of molliiscan shell . . 21 



3. Nacre laminae in surface view .... 23 



4. Anatomy of Ceylon pearl oyster .... 28 



5. Positions of muscle pearls in Ceylon pearl oyster . 55 



6. Section of pearl (prismatic) 57 



7. Section of pearl (nacreous) 59 



8. Nemertine worm imbedded in nacre ... 86 



9. Diagrams showing formation of pearl in Mytilus . 103 



10. Section of larval worm in Ceylon pearl oyster . 105 



11. Teirarhynchus unionifactor 105 



12. Diagi-ams of development of pearl sac . . . 113 



