v1 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 unificd 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 mercly as an outline 
