vill PREFACE 



I regard the studies recorded in this volume as the mere 

 beginnings of work which should be developed. I dare say 

 that our record contains many imperfections and possibly 

 some errors. Future studies will perfect the former and elimi- 

 nate the latter. Attempts to solve the problems stated in 

 this volume have occupied many years and filled them with 

 the interest and pleasure that always come to those who 

 seek to widen the fields of the known. 



THE SENIOR AUTHOR. 



ANN ARBOR, 1913. 



