133 THE < EICAGO ACADEMY OF SCIENCES. 



the center along the line of the columellar muscle, the respiratory tract 

 may be examined entire. The central nerve mass will be observed 

 just behind the buccal sac. Care must be used in separating the dif- 

 ferent organs, in order not to tear them. This is especially true of 

 the genitalia. The jaw and radula may be extracted from the front 

 end of the buccal sac and mounted in Canada balsam or glycerine jelly 

 for study. The writer has frequently used a two-inch and one-inch 

 objective for working out the details of anatomy, and has found it 

 very satisfactory in many cases, the only drawback being the inability 

 to use both hands in separating the organs. Dissected specimens may 

 be permanently preserved in 75% alcohol. 



A large amount of work is badly needed to provide additional 

 information relating to the anatomical features of the fresh-water 

 pulmonates, and almost any careful student may add valuable data 

 concerning the affinities of the different species. There are a number 

 of species which cannot be definitely placed, owing to lack of knowl- 

 edge concerning the radula, jaw and genitalia. Too much emphasis 

 cannot be placed on the admonition to be accurate in studies of this 

 kind, because serious errors have been made by a too hasty statement 

 regarding some anatomical feature. 



