PREFACE TO THE SECOND EDITION. 



IN preparing this edition many changes have been 

 made; every page has been revised and some errors 

 corrected. Several new illustrations have been added 

 and directions for the study of other animals have been 

 inserted. As in the first edition, greater prominence has 

 been given to the vertebrate than to the non-vertebrate 

 forms, since experience has shown that the work has been 

 largely used as an introduction to or preparation for 

 medical studies. The greatest change, however, has been 

 in the separation of the laboratory work from the de- 

 scriptive part of the text. Still, the pedagogica" advan- 

 tages of the former arrangement have been maintained 

 by numerous cross-references, while the systematic portion 

 has a continuity which was lacking in the former edition. 



In the illustrations care has been taken to figure noth- 

 ing which is studied in the laboratory. Students have 

 been known to copy drawings rather than to work the 



details out from the specimen. 

 TUFTS COLLEGE, MASS., June, 1904. 







^^^^^H 111 



