X AUTHOR'S PREFACE 



The author is indebted to Miss Helen Snyder for the care 

 with which many of the drawings have been made. While the 

 drawings, except as acknowledged in the text, have been made 

 from the specimens, suggestions as to methods of expressing 

 essential characters have been taken at times from the books 

 mentioned in the Hst at the end of the volume. The author 

 gratefully acknowledges his indebtedness. 



A few of the half-tone illustrations are from negatives in the 

 collection of the School of Education, for the use of which the 

 author expresses his indebtedness. 



Elliot R. Downing 



University of Chicago 



School of Education 



December 27, 1921 



