THE society's NOTE-BOOKS. 83 



insects. Some authorities object to the popular term "tongue," 

 and prefer the long word " odontophore." 



It would appear from the testimony of several investigators of 

 these beautiful objects, that they by no means invariably determine 

 the species, " although the patterns or types of the lingual mem- 

 branes are, on the whole, remarkably constant, yet their systematic 

 value is not uniform, and therefore the attempts to remodel the 

 Gasteropods by their peculiarities of dentition have not become so 

 complete a success as teas at first expected ^ 



Dr. Troschel, who has written a good deal on the subject, 

 classifies the principal types by means of their lingual dentition, 

 but the generic characters of each have yet to be ascertained. In 

 the Patella radiaia the teeth are very strong and numerous, being 

 also nearly opaque ; those of the Trochus are also very numerous, 

 but the band is much wider, and " not only are the large teeth of 

 the lateral bands very beautiful, but the delicate leaf-like teeth of 

 the central portion have their edges minutely serrated." 



The preparation of these palates is by no means easy. You 

 have to " first catch your hare " — that is, you have to dissect the 

 object from its surroundings, which are all of a slippery, slimy 

 nature. Obviously, the dissection must be done under water. 

 The first touch of the knife or forceps will in most cases have the 

 happy effect of making the water so turbid that nothing can be 

 seen. The water must then be changed, and the process will have 

 to be repeated several times. Hogg gives the following method: — 

 " The animal having been taken from its shell, pin down the mus- 

 cular foot to a piece of cork, pour water upon it ; then with a dis- 

 secting microscope and a good bull's-eye condenser cut open and 

 expose to view the floor of the mouth ; pin back the cut edges 

 throughout its entire length, and work out the dental band with 

 knife and forceps. When the band is detached, place it in a 

 watch-glass, and again clean it well by repeated washings and a 

 camel's hair brush ; then place it in weak spirit and waiter, where 

 it must remain for a few days before mounting. If the membrane 

 is dense and fatty, it must be soaked for a time in liquor potassae, 

 and when removed carefully washed. The best fluids for mounting 

 are weak spirit and water, glycerine, glycerine jelly, or Goadby's 

 solution. Canada balsam renders them so very pellucid that the 

 finer teeth are completely lost in it." 



