iv PREFACE. 



naturalists, but no really important step toward organ- 

 izing the teaching of biology in accordance with it had 

 previously been taken. 



In the past five years, during which I have been 

 responsible for the direction of biological studies in 

 the Johns Hopkins University, I have endeavored to 

 arrange the curriculum so as to ensure that each stu- 

 dent, before taking up any one branch of biology for 

 special study, shall have acquired a fairly good knowl- 

 edge of what may be called general biology. No un- 

 dergraduate is permitted to devote his time to the 

 study of botany, or animal morphology or physiology, 

 until he has spent at least one year in learning some- 

 thing about animals and plants in general. Such a 

 course is indisputably far better than one more specially 

 botanical or zoological for those who merely desire 

 some knowledge of biological science as a part of 

 general education ; and I have been yearly more firmly 

 convinced that it affords also the best beginning for 

 the student who desires to become ultimately a botanist, 

 zoologist, or physiologist. 



While the general structure of all plants can be fairly 

 well understood after the careful examination of a small 

 number of selected types, this is not the case with ani- 

 mals ; and I have accordingly found it necessary to 

 include in the annual course several types, especially 

 vertebrate, not described in the ''Practical Biology." 

 Of these a Chelonian is much the most difficult to dis- 



