THE MOLLUSCAN RADULA. 115 



The MoUuscan Radula: its Chemical Composition, 

 and Some Points in its Development. 



By 

 Igerna B. J. Sollas. 



With Plate 9. 



History. 



The molluscan radula, or dental ribbou, has been the sub- 

 ject of research for at least a century and a half. Aristotle (3), 

 though he speaks of teeth in Limax, alludes apparently 

 to the lidges on the jaw, and there is no evidence that he 

 knew of the existence of the radula : but it is interesting' to 

 find that the great naturalist was well aware of the fact that 

 Avhelks bore holes in shells with the proboscis, although he 

 cannot have fully understood the process. Poli made a jest 

 of the tale as a fable, but Osier re-affirmed it in 1832 without 

 knowing of previous work, and is now credited with having 

 been the first to observe this interesting habit. 



Swammerdam is the discoverer of the radula : he gives a 

 description of both the radula and jaw of the snail (Helix 

 aspersa), in Dutch and Latin, in his 'Biblia Naturse,' 

 Ley den, published posthumously. His death, as we are told 

 by Boerhaave in the Life of the author prefixed to this work, 

 occurred in 1680. The work is now too antiquated to possess 

 more than an historical interest. 



Hi 1757 Adanson (1) described radulse from various 

 gastropods of Senegal : the teeth are " infinitely small, hardly 



