PREFACE. 



SEVEEAL years ago it was our good fortune to follow as grad- 

 uate students a course of lectures and practical study in General 

 Biology, under the direction of Professor Martin, at Johns Hop- 

 kins University. Since that time we have ever been strongly of 

 the opinion that beginners in Biology should be introduced to 

 the subject by some similar method, following iu the main the 

 outlines marked out by Huxley and Martin more than ten years 

 ago. The present work thus owes its origin to the influence of 

 the authors of the "Elementary Biology," our deep indebtedness 

 to whom we gratefully acknowledge. 



It has not been our ambition to prepare an exhaustive trea- 

 tise. We have sought only to lead beginners in biology from 

 familiar facts to a better knowledge of how living things are 

 built and how they act, such as may rightly take a place in 

 general education or may afford a basis for further studies in 

 General Biology, Zoology, Botany, Physiology, or Medicine. 



It is still an open question whether the beginner should pur- 

 sue the logical but difficult course of working upwards from 

 the simple to the complex, or adopt the easier and more practi- 

 cal method of working downwards from familiar higher forms. 

 Every teacher of the subject knows how great are the practical 

 difficulties besetting the novice, who, provided for the first time 

 with a compound microscope, is confronted with Yeast, Proto- 

 coccus, or Amoeba ; and on the other hand, how hard it is to sift 

 out what is general and essential from the heterogeneous details 

 of a mammal or a flowering plant. In the hope of lessening the 

 practical difficulties of the logical method we venture to submit 

 a course of preliminary study, which we have used for some 

 time with our own classes, and have found practical and effec- 

 tive. Believing that biology should follow the example of phys- 

 ics and chemistry in discussing at the outset the fundamental 



