XXXVl PREFACE TO THE THIRD EDITION. 



of human tribal history, can be based. And yet, as Baer 

 says, ''no investigation is more worthy of a free and 

 thoughtful man than the study of himself." (Cf. vol. i. 

 p. 244.) Hoping, as I do, that I may have aided to some 

 extent to bring about this true self-knowledge, I shall have 

 gained my purpose if my labours arouse an active interest 

 in wider circles in the historic evolution of our animal 

 organism, and if they advance the knowledge of this most 

 significant process. 



Ernst Heinrich Haeckel. 



Jena^ October 6, 1876. 



