This work, which is here present in the English language, is based on a course of lectures given at the University of Helsingfors, Finland, during the academic year 1916-17. It is the author's intention to present a picture of the development of biological science throughout the ages, viewed in conjunction with the general cultural development of mankind. Regarded thus as a link in the general history of culture, the problems of biology will, it is hoped, prove of interest not only to young university students, for whom this book is primarily intended, but also to a still wider public. With regard to moderen times, for obvious reasons it has only been possible in such a brief history as this to give a very summary account of recent developments.