The present work is a plain study of the personality of Haeckel and the growth of his ideas. The character of Haeckel was forged amid circumstances that have largely passed away from the scientific world of our time. The features, even, of the world he has worked in of recent years in Germany are so different from our own that no Englishman can understand him without sober study of his life. He has often been called “the Darwin of Germany.” The phrase is most misleading. It suggests a comparison that is bound to end in untruth and injustice. In the same year that Haeckel opened his Darwinian campaign in Germany he won the prize for the long jump—a record jump. It is the note of much in his character. He was no quiet recluse, to shrink from opposition and hard names, but a lusty, healthy, impetuous, intrepid youth, even when his hair had worn to grey. A story is told of how, not many years ago, the Grand Duke of Weimar playfully rallied him, in the midst of a brilliant company, on his belief in evolution. To the horror of the guests, he slapped the powerful noble on the shoulder, and told him to come to Jena and see the proofs of it. In his seventy-first year we find him severely censuring his Emperor—the emperor of many fortresses—in a public lecture at Berlin. How his vigour and his resentment arose as barrier after barrier was raised before him: how his scorn of compromise was engendered and fed: how he accumulated mountains of knowledge in obscure, technical works before he formulated his sharp didactic conclusions: all this is told in the following story. For good or ill he has won an influence in this country, and his story should be read. It is, in itself, one of rare and varied interest, and it is told by one of the most brilliant penmen of modern Germany, his former pupil, now a distinguished biologist, Professor Wilhelm Bölsche.