DIGESTIVE ORGANS. 97 



are therefore mostly mdividual counts which may vary somewhat 

 in other specimens of the same species. 



Rev. G. Rowe observes that * " this subject has been investi- 

 gated by several naturalists, with a view to obtaining criteria for 

 a systematic arrangement of Gastropodous Mollusca. Up to the 

 present time, however, their labors have only partially succeeded. 

 The union under one formula of so many creatures widely 

 dift'ering in shells, anatomy and habits, clearly indicates that if 

 the lingual ribbon contains generic characters, they have not j^et 

 been ascertained. At the same time it does present differences 

 which may offer collateral evidence in cases difficult of discrimi- 

 nation. It does not help us to discriminate carnivorous from 

 phj'tophagous animals ; but it seems possible to make use of it 

 as a mark between species." 



On Ext7'acting and Preserving Odontophores. If the specimens 

 are large enough, the head may be opened from above, exposing 

 the buccal mass, which lies close under the skin ; this is easily 

 cut away from the animal, and will be found to contain both jaw 

 (when it exists) and lingual membrane. These can be removed 

 by 'fine scissors or knives, but in the smaller species the whole 

 buccal mass, or even the entire animal with the shell may be 

 placed in a test tube, immersed in Liquor Potassas, 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 bottom, whence 

 it must be carefully taken out by means of a dip-tube and 

 thoroughly washed until all alkali is removed. Alcoholic speci- 

 mens require boiling in the alkaline solution, but fresh material 

 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 

 glycerine), but in mounting as a microscopic object, glycerine- 

 gelatine should be used. Canada balsam ruins the membrane 

 by rendering it too transparent.f 



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 multi- 



* Intellectual Observer, v, 67, 1864. 



f A. M. Edwards, Proe, N. T Lye, 160; W. G. Binney, Bull. Mus. 

 Comp. Zool., iv, 42. 



