INTRODUCTION 13 



freely on another biographical sketch by one of 

 Haeckel's pupils, Dr. Breitenbach, and other sources. 

 For the illustrations I am indebted chiefly to 

 Professor Haeckel himself, and can only offer 

 him in return this grateful effort to lift his in- 

 spiring and impressive personality above the dust 

 and cloud of a great controversy. 



JOSEPH McCABE. 



