28 DIGESTIVE ORGANS. 



chitinous material and six per cent, of bone-earth, agreeing 

 nearly with horn in composition. They are readily extracted 

 and prepared as microscopic objects, the easiest method of pro- 

 cedure being that given by Mr. A. M. Edwards, which I subjoin. 



On extracting and preserving Odontophores. If the specimens 

 are large enough, they may be first roughly out away from the 

 surrounding tissues; otherwise the entire animal, even with the 

 shell may be placed in a test tube, immersed iu Liquor Potassae. 

 and allowed to soak from a day to several weeks until everything 

 is dissolved except the shell, the odontophore and a few shreds 

 of muscular fibre. The contents of the tube being poured into a 

 large vessel of clean water, the odontophore will settle to the bot- 

 tom, whence it must be carefully taken out by means of a dip" 

 tube and thoroughly washed until all alkali is removed. Alcoholic 

 specimens require boiling in the alkaline solution, but fresh ma- 

 terial had better be treated cold, unless time presses, when boiling- 

 will facilitate the extraction of the odontophore. In this case 

 care must be taken as delicate specimens are likely to be injured 

 by boiling. When the specimens are very delicate, a solution of 

 less than officinal strength is substituted with advantage: this is 

 a matter in which experience is the best teacher. 



The odontophore can be preserved (in either alcohol or glyc- 

 erine), but in mounting as a microscopic object Canada bnlsam 

 or still better, glycerine-gelatine should be used." 



Through Troschel, in 1836, attention was first directed to the 

 various forms of tongue sculpture as being available in classifi- 

 cation, and Loven and Troschel himself by means of the 

 most exhaustive investigations discovered the extraordinary 

 multiplicity of form, etc., of the radula. In their syste- 

 matic labors Troschel and Gray raised the r#dula to the rank of 

 a character of the first importance, in the molluscan, especially 

 the gasteropod system, and they accordingly made many changes, 

 rearrangements, and improvements. 



To be sure, the tongue and its delicate teeth have been long 

 since known, but they occupied only a subordinate place in the 

 minds of systematists. With Lebert we might agree that Aris- 

 totle meant the teeth upon the radula (Hist. Aniin. vi, 4.) 



* A. M. Edwards, Proc. N. Y. Lye., 160. 



