VI PREFACE 



suited but none followed consistently. In the interest of the 

 beginner simplicity is desirable and to this end a number of 

 unimportant, obscure or aberrant groups have been omitted 

 and only three grades, or orders of groups, recognized, viz., 

 Branch or Phylum, Class, and Order. The classification of 

 animals given in the "Lehrbuch" of Claus-Grobben has been 

 followed more closely than that of any other author. 



Acknowledgment is due the publishers, Messrs. P. Blakis- 

 ton^s Son & Co., for the loan of many figures from the works 

 of Galloway, Stevens, Folsom and others. The Macmillan Co. 

 and Henry Holt and Co. have also kindly furnished several 

 figures. More specific acknowledgment is made in connection 

 with each borrowed figure. 



J. I. HAMAKER. 

 COLLEGE PARK, VA. 



