DIRECTIONS TO THE INSTRUCTOR 
The exercises in this book are so planned that they may be 
adapted to various forms of presentation, to schools whose labo¬ 
ratory equipment is complete or meager, and to the varying 
conditions of climate and of community life where the guide 
is to be used. In general, it is advised that the work be done 
in the field when it is so suggested; that the demonstration 
method of presentation be employed in the majority of the exer¬ 
cises (see Downing, Teaching Science in the Schools, Chapter 
VIII, University of Chicago Press, 1925); and that the textbook 
and these laboratory exercises be regarded as supplementary 
to each other. 
Early in the year the instructor should carefully note what 
materials are required for the exercises which he plans to use. 
He should then make provision for them by the collection and 
preservation of such material and by placing early orders with 
supply companies when additional material is needed. No¬ 
tations are made at appropriate points in the Manual to remind 
the instructor of such material as must be prepared immediately 
before it is used. 
It is advised that where microscopic studies are to be made 
by students of secondary schools, the manipulation of the micro¬ 
scope and the preparation of slides should both be cared for by 
the instructor. The use of a projection microscope will greatly 
facilitate such studies and will add much to the efficiency of 
instruction. 
If studies of the internal anatomy of animals are desired, the 
use of specimens previously dissected and prepared by the instruc¬ 
tor or of museum dissections (which are permanently mounted 
and may be obtained from supply houses) is recommended. 
The use of such preparations obviates the current objections 
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