284 MICROSCOPY FOR BEGINNERS. 



a band- like body having many rows of short, variously 

 formed teeth, which, under the microscope, present a 

 beautiful and dazzling appearance. It is situated so 

 that it may be partially protruded and used as a file, 

 which not only removes the food particles, but carries 

 them into the mouth. It may be obtained from any 

 of the pond-snails, either by dissecting it out under the 

 microscope with needles a tedious process, successful 

 in the hands of advanced workers or by dissolving the 

 soft parts of the snail by boiling the animal in a solution 

 of caustic potassa. Drop the snail into a test-tube con- 

 taining a small quantity of the solution, and boil until 

 all of the soft body has disappeared. "When cold pour 

 off the liquid very gently, and the lingual ribbon will 

 be found at the bottom usually without trouble, although 

 it is often small and always perfectly transparent. The 

 last few drops may be poured on a slip and examined 

 with a low power, when the lingual ribbon will be seen 

 and can be isolated with a needle. The form, size, and 

 arrangement of the teeth vary greatly in the different 

 water-snails. To see them is worth all the trouble that 

 their preparation seems to demand. The ribbons should 

 be examined in water or glycerine. A high power will 

 often be required to show the teeth well. 



13. The delicate epidermis from the leaves of plants 

 can be obtained at any time in an unlimited supply and 

 variety in summer from the wild plants, in winter from 

 those cultivated in the house. The cells forming this 

 thin and usually colorless membrane vary in form and 



