viii PREFACE 



Finally, let it be repeated that it is much better for the 

 beginning pupil to acquire a real conception of a few 

 central principles and points of view respecting common 

 forms that will enable him to tie his knowledge together 

 and organize it and apply it, than to familiarize himself 

 with any number of mere facts about the lower forms of 

 life which, at the best, he can know only indirectly and 

 remotely. If the pupil wishes to go farther in later years, 

 he may then take up special groups and phases. 



