vi PREFACE 



audiences at the Wagner Institute encourages me 

 to hope that a larger and more widely dispersed 

 audience may share the same interest. The annoy- 

 ing barrier of technical language has been evaded 

 so far as possible, but the lack of suitable vernacular 

 terms is such that it is not practicable to escape 

 technicalities altogether. The effort to use ordinary 

 speech and the want of numerous illustrations have 

 caused a certain prolixity of description, which is 

 regrettable, but less so, perhaps, than the alternative 

 of obscurity. 



My experience with graduate students of biology 

 has shown me that usually their training has so com- 

 pletely taken for granted the truth of the evolu- 

 tionary doctrine, that they have but a vague con- 

 ception of the testimony by which that doctrine 

 is supported. This book may be useful in directing 

 their attention to the character of the evidence and, 

 though, of course, the meagre sketch contained in 

 these lectures is entirely inadequate in itself, it does 

 provide an outline which students can easily fill in 

 from their own reading. 



In the winter of 1910-11 an admirable series of 

 popular lectures by several men of high distinction 

 was delivered in the Natural Science Society of 

 Munich, as a tribute to the centennial of Charles 

 Darwin's birth. These lectures were published in 

 1911 by G. Fischer of Jena with the title Die Abstain- 

 mungslehre. To this most excellent compendium 

 of the evidences of evolution I am under great ob- 



