PREFACE 7 



to make careful drawings of the objects studied. Wherever 

 time permits, the laboratory work outlined here should be 

 expanded by instructors. (For more detailed laboratory di- 

 rections than can be given here, reference should be made to 

 the many excellent handbooks of zoological and botanical lab- 

 oratory work, a few of which are mentioned in the brief bibli- 

 ographies at the close of the chapters.) 



In place of the ordinary index there will be found at the 

 close of the book a glossary-index. In it are given brief defi- 

 nitions of all the technical words used in the book, with deri- 

 vations and with page references. To make this more valuable 

 as a reference glossary, some common biological words which 

 do not chance to be used in the text are defined. These are 

 easily recognized from the fact that they have no page numbers. 



H. W. CONN. 



