IV PREFACE. 



properties of matter and energy, we have devoted the first four 

 chapters to an elementary account of living matter and vital en- 

 ergy. In the six chapters which follow, these facts are applied 

 by a fairly exhaustive study of a representative plant and animal, 

 of considerable, though not extreme, complexity a method which 

 we believe affords, in a given time, a better knowledge of vital 

 phenomena than can be acquired by more superficial study of a 

 larger number of forms. "We are satisfied that the fern and 

 earthworm are for this purpose the best available organisms, and 

 that their study can be made fruitful and interesting. The last 



/ < ' 



chapter comprises a brief account of the principles and outlines 

 of classification as a guide in subsequent studies. 



After this introductory study the student will be well pre- 

 pared to take up the one-celled organisms, and can pass rapidly 

 over the ground covered by. such works as Huxley and Martin's 

 Practical Biology ^ Brooks's Handbook of Invertebrate Zoology, 

 Arthur, Barnes and Coulter's Plant Dissection, or the second 

 part of this book, which is well in hand and will probably be 

 ready in the course of the following year. 



The directions for practical study are intended as suggestions, 

 not substitutes, for individual effort. We have striven to make 

 the work useful as well in the class-room as in the laboratory, 

 and to this end have introduced many illustrations. The gener- 

 osity of a friend has enabled us to enlist the skill of our friend 

 Mr. James H. Emerton, who has drawn most of the original 

 figures from nature, under our direction. We have also been 

 greatly aided in the preparation of the figures by Mr. William 

 Claus of Boston. 



NEW YORK, September, 1886. 



