vi PREFACE 



been given at the close of the volume, that will enable readers 

 who wish fuller information to go to the best sources. 



The book is divided into two sections. In the first are 

 considered the sources of the ideas except those of organic 

 evolution that dominate biology, and the steps by which 

 they have been molded into a unified science. The Doc- 

 trine of Organic Evolution, on account of its importance, 

 is reserved for special consideration in the second section. 

 This is, of course, merely a division of convenience, since 

 after its acceptance the doctrine of evolution has entered 

 into all phases of biological progress. 



The portraits with which the text is illustrated embrace 

 those of nearly all the founders of biology. Some of the 

 rarer ones are unfamiliar even to biologists, and have been 

 discovered only after long search in the libraries of Europe 

 and America. 



An orderly account of the rise of biology can hardly fail 

 to be of service to the class of inquirers mentioned in the 

 opening paragraph. It is hoped that this sketch will also 

 meet some of the needs of the increasing body of students 

 who are doing practical work in biological laboratories. It is 

 important that such students, in addition to the usual class- 

 room instruction, should get a perspective view of the way 

 in which biological science has come into its present form. 



The chief purpose of the book will have been met if I 

 have succeeded in indicating the sources of biological ideas 

 and the main currents along which they have advanced, and 

 if I have succeeded, furthermore, in making readers ac- 

 quainted with those men of noble purpose whose work has 

 created the epochs of biological history, and in showing that 

 there has been continuity of development in biological 

 thought. 



Of biologists who may examine this work with a critical 

 purpose, I beg that they will think of it merely as an outline 



