132 THE CHICAGO 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. 
