iv PREFACE 
not depend upon any others. The teacher is thus enabled to 
give his class such dissections as he wishes and is not compelled 
to adopt the entire series in order to have his course complete. 
In my own classes, I vary the order of the dissections from 
year to year and never go through the entire course. I even 
occasionally begin the course with the Protozoa and work 
upward to the higher animals; but I do not consider this 
usually so profitable a method of procedure for the pupil as 
the one herein recommended. 
An important feature of the plan of this course has been 
adopted, in a somewhat different form, from Huxley and 
Martin’s “ Practical Biology ”’ and Marshall and Hurst’s “ Prac- 
tical Zodlogy.” It is to give the student such practical directions 
that he can go on with his work intelligently and profitably 
without having an instructor constantly at his elbow. It has 
been my experience that far too much of the time of the average 
youthful student is often wasted in the laboratory because the 
instructor does not happen to be at hand at critical times to 
direct his work. The student will often do the work wrong 
in consequence, or perhaps he will not do anything at all; in 
either case his time is wasted and perhaps his material spoiled. 
In most of the dissections the directions are so arranged that 
the student can complete the study with a single specimen, and 
the order in which the different systems of organs are taken up 
in each dissection is made dependent upon this feature. The 
necessity of practicing economy of material is thus inculcated, 
and the habit is acquired of studying and handling each 
specimen with care and judgment. 
I have been fortunate in procuring the codperation of a num- 
ber of well-known teachers in the revision of the proofs, with 
the aid of whom I have sought to eliminate errors so far as 
possible. Portions of the proofs have been read critically by 
