DKiEHTlVK ORGANS. 29 



'' habent qiupdam os et dcntes, ut Limax, acutos et minutos," 

 and not as Loven held, the jaws, but we meet with a better ac- 

 count of them for the first time in Sw.-tuimeidam ujion Paludina, 

 Littorina and Neritina. 



Witli many other striking observations upon niollusks we 

 meet with tlie tirst descri[)tion of the raduhi in Adanson, 

 whieli with the undei'lying tongue he regards as a lower jaw. 

 ''La machoire inferieure,'' writes Adanson {Hist. Nat. du Seneg. 

 p. IT) in a Bulimus, his B. Kambeul, '• ne consiste que dans le 

 l)alais inferienr de la bouehe, qu'est tapise d'une membrane 

 coriace, mais extremement minee, blanche et transparente, sur 

 laquelle sont distribues longitudinalement sur deux cens rangs 

 environ vingt mille dents seniblables a autant de crochets cour- 

 bes en arriere. Ces crochets sont si petits qu'on a peine a les 

 sentir au toucher, on ne les distingue ])arfaitement qu'au micro- 

 scope." 



Poll was one of the fii'st to ligure tlie raduhe of (Jephalopods. 

 (iasteropods and Chiton, then Savign3' in his Zoology of the 

 Description de I'Egypte. Cuvier in his Memoires correctly de- 

 scribes the radulae of a number of mollusks, but attached 

 little systematic value to the part. On the other hand Quoy and 

 (jaimard, and Soulevet in the works describing the collection of 

 their voyages, tigure many radula*. but they Avere not brought 

 forward with sufficient i)rominence. In Osier's work on the 

 mode of feeding of mollusks, attention was again more especially 

 directed to the radula*. and Lebert studied the same more par- 

 ticularly with reference to tlieii' microscopic characters. As 

 already observed, the extensive observations of Loven and 

 Troschel are the most compiehensive in their treatment of tiie 

 subject of this discussion, thougii the great work of the latter 

 approaches completion veiy slowly. We shall hereafter sketch 

 an outline of the classifications which liave been wholly or |)ar- 

 tially based upon modifications of tlie odontophore. 



The tongue, beset with such teeth, is well adapted as an ap- 

 paratus for filing off or rasping food and drawing it into the 

 mouth. Li mollusks which creep up on the glass sides of a 

 vessel in which they are confined, one can easily observe the 

 mechanism of eating. The tongue with the whole oral mass is 

 pushed forward a little beyond the lips, so that one can see the 



