APPENDIX. 
The following directions for experiments and dissections are 
given for the purpose of enabling the teacher and pupil to make 
direct observation of the structure and functions of certain ani¬ 
mals which may be considered to represent in a general way the 
groups to which they belong. The tendency of modern teach¬ 
ing of Zoology is to have the student learn as much as possible 
by personal investigation. In a general course of Zoology, for 
which this book is designed, it is not practicable to introduce 
very much study of the specimens themselves. However, 
enough such observational work should be performed to give 
the pupil knowledge of the general structure of the more im¬ 
portant groups of animals, as well as of the functions of their 
bodily organs. 
The experiments and dissections are purposely chosen with a 
view to their simplicity, and to the ease with which they may 
be performed. Constant reference is made to figures which will 
both guide and illustrate the dissections. More extended stud¬ 
ies may be carried out with the aid of the various works men¬ 
tioned on pages 397, 398. 
CHAPTER II. 
The difficulty of distinguishing by ocular observation alone 
the lower animals from the lower plants may be illustrated by 
making a microscopic examination of drops of sediment from 
the bottom of a stagnant ditch. The water will probably be 
teeming with unicellular organisms, both animal and vegetable, 
which cannot be differentiated by characters of form, size, color, 
motion, etc., alone. 
