48 



HOMES UNDER THE SEA. 



technical name for these papillae is " ambulacra," from the 

 Latin word ambulare, to walk. 



Their structure is remarkably beautiful, but the me- 

 chanical contrivances which render them capable of pro- 



Fig. 2. UNDER SURFACE OF THE FIVE-FINGERED STARFISH. 



trusion, retraction, adherence, and detachment, are so 

 complicated that they cannot be easily described. Suffice 

 it to say that along the under surface of the body are a 

 number of hard, shelly shields, set closely side by side, 



