Vlll 
PREFACE 
finished artistic effect, is not only inadvisable from the standpoint 
of time, but often leads to a sacrifice of scientific accuracy. 
In the preparation of the second edition of the book a consider¬ 
able rearrangement of the subject matter has been made because 
in the actual use of the book at Smith College the various instruc¬ 
tors have found that such a rearrangement constituted a more 
logical development of the subject as well as a more convenient 
method of administering the course. For these suggestions and 
many others which have been embodied in the revision I wish 
here to express my gratitude to the former and present members of 
the Department of Zoology of Smith College who have been my 
colleagues in the teaching of this course. 
Inez Whipple Wilder. 
Smith College, Northampton, Mass. 
