v i PREFACE 



be connected with any knowledge of the subject, however 

 vague, he may already possess, the better for his progress. 



On the other hand, the advantage to logical treatment of 

 proceeding from the simple to the complex of working 

 upwards from protists to the higher plants and animals is 

 so immense that it is not to be abandoned without very 

 good and sufficient reasons. 



In my own experience I have found that the difficulty 

 may be largely met by a compromise, namely, by beginning 

 the work of the class by a comparative study of one of the 

 higher plants (flowering plant or fern) and of one of the 

 higher animals (rabbit, frog, or crayfish). If there were no 

 limitations as to time, and if it were possible to avoid alto- 

 gether the valley of the shadow of the coming examination, 

 this preliminary work might be extended with advantage, and 

 made to include a fairly complete although elementary study 

 of animal physiology, with a minimum of anatomical detail, 

 and a somewhat extensive study of flowering plants with 

 special reference to their physiology and to their relations 

 to the rest of nature. 



In any case by the time this introductory work is over, 

 the student of average intelligence has overcome pre- 

 liminary difficulties, and is ready to profit by the second 

 and more systematic part of the course in which organisms 

 are studied in the order of increasing complexity. 



It is such a course of general elementary biology which 

 I have attempted to give in the following Lessons, my aim 

 having been to provide a book which may supply in the 



