968 FRESH-WATER BIOLOGY 



thus brought into view, and further dissection of the organs can 

 be inteUigently made."-^ 



The method of preparing the jaws and hngual membrane for 

 examination is as follows: 



''On opening the head (of the snail) from above, one readily 

 notices at the extreme anterior part, close against the outer integu- 

 ment, a prominent, oval body. This is called the buccal mass. It 

 is easily cut away from the animal, and will be found to contain 

 both jaw and lingual membrane. These can be removed by fine 

 scissors or knives from the buccal mass in the larger species, but 

 in the smaller species, the method usually employed is putting 

 the whole buccal mass in a watch crystal, full of a strong solution 

 of caustic potash. Allowing it to remain for several hours, the 

 potash will destroy all of the buccal mass, and leave the jaw and 

 lingual membrane perfectly clean and ready for examination. 

 They must be well rinsed in clean water, in another watch crystal, 

 before examination. Another more expeditious process, is to place 

 the whole buccal mass in a test tube with the solution of potash, 

 and boil it for a few seconds over a spirit lamp. Pouring the con- 

 tents of the tube into a watch crystal, the lingual membrane at- 

 tached to the jaw will be readily seen by a pocket lens. If the 

 species be small, its whole body may be thrown into the solution. 

 Still more minute species, may be treated in this way; crush the 

 whole shell between the glass sHdes; wash the particles of broken 

 shell in a few drops of water, still keeping the body of the animal 

 on the slide; when clean, drop on it the caustic potash and boil it 

 by holding the sHde itself over the spirit lamp. 



"For purpose of examination, the jaw and Ungual membrane 

 may be simply mounted in water and covered with thin glass. One 

 must be sure in spreading out the lingual membrane not to have 

 its upper side down, and it is well to cut it transversely in several 



^ No detailed instructions for the dissection of the fresh-water moliusks have been 

 published in this country. For an admirable, fully illustrated paper on the dissection 

 of the land snail, which can be easily adapted for the use of the student, see Simpson, 

 Bull. N. Y. State Museum, viii, p. 241 (1901;. The same author has published an 

 excellent study, fully illustrated, of the anatomy of Anodonta, which should be in the 

 hands of every student. See Rep. N. Y., State Mus. of Nat. Hist., 35, p. 169. 



