GROWTH OF IDEAS 291 



tree of the living world, branch by branch, and, 

 with the material that had accumulated in the 

 subsequent thirty-four years, built it up into a 

 iseparate work. It had consisted formerly of 160 

 pages : now it formed three volumes of 1,800 pages. 

 There were forty years of incessant study embodied 

 in it. It had the title Systematic Phylogeny : * 

 " a sketch of a natural system of organisms on the 

 basis of their stem-history." The first volume 

 (dealing with the protists and plants) appeared in 

 1894 ; the second volume (dealing with the in- 

 vertebrate animals) in 1896, and the third (dealing 

 svith the vertebrates) in 1895. Closely connected 

 fllth it is his special systematic study of the 

 item-history of the echinoderms (star-fish, &o.), 

 ,vith particular reference to paleontology (The 

 imphoridea and cystoidea in the Work in Com- 

 nemoration of Karl Gegeribaur, 1896). 



His academic colleagues had hardly begun to 

 naster this new phylogeny when Haeckel once 

 nore roused a general agitation by working up the 

 >hilosophic nucleus of the Morphology in a more 

 general form than he had done in the History of 

 Creation. This new work was The Riddle of the 

 Jniverse, " a popular study of the Monistic philo- 

 ophy." t It was, he declared, his philosophical 

 estament. In a few months 10,000 copies of the 

 fork were sold, and a later cheap popular edition 



* It has not been translated into English. A recent re- 

 iewer in Nature pronounced it to be Haeckel's best work. 

 Trans.] 



t Literally, the title is " World-Biddies," or " World- 

 robleins." [Trans.] 



