136 IGEHNA B. J, SOLLAS. 



Fig. 6. — Lateral teeth of Nacella sp. <?, Outer ; i, iiiuer lateral tooth. 

 The portion a" becomes isolated (by boiling acid) from a, leaving n . 



Fig. 7. — A lateral tooth of Chiton sp. isolated from the radula by the 

 action of strong cold nitric acid, showing the hollow chitinous basal portion 

 and the brown cusp which contains iron oxide. 



Fig. 8. — Portions of the radula of Patella vulgata in order of succession 

 {a — d) from the radula sac to the mouth cavity. Bethe's stain and carmalum. 



Fig. 9. — Portions of the radula of Li ttorina littorea in order of suc- 

 cession {a — d) from the radula sac to the mouth-cavity. Belhe's stain and 

 eosin. 



Fig. 10. — Portions of the radula of Buccinum undatum in order of 

 succession {a — d) from the radula sac to the mouth-cavity. Bethe's stain and 

 eosin. 



Fig. 11. — A rough sketch of a strip of the radula ofTrochusziziphinus 

 including the marginals and laterals of three rows of one side. Stained with 

 carmalum. 



Fig. 12. — Isolated teeth teased out of a radula of Trochus ziziphinus 

 which had been previously stained with hsematoxylin. 



Fig. 13. — Eight teeth from two rows of the radula of Helix aspersa, in- 

 cluding two centrals. Bethe's stain and eosin ; surface view. 



Fig. 14. — Two teeth and the underlying basal membrane of Helix 

 aspersa in longitudinal section. Bethe's stain and safranin. 



Fig. 15. — Three teeth and the underlying basal membrane of Helix 

 aspersa in longitudinal section. Stained with safranin only. 



