Fig. 30. Explanation of Fkjukes of Sand-dollar. 



1. Diagram of one fifth of Aristotle's lantern of Doidrasfcr show- 

 ing three loops of the circumoral nerve ring, and parts of three 

 radial nerves, the central one partly hidden at its origin by the 

 lantern. The nerves are in black. X9. 



2. Drawing of part of the first part of an oral radial nerve. X9. 

 8. Drawing of the lower end of an oral radial nerve. X9. 



