DARWIN 137 



there was no eternal Deity and that spontaneous 

 generation itself was by no means a forbidding 

 conception. The problem for him was merely, 

 how he could work upward through the plants and 

 animals of all geological periods until he reached 

 man. He was bound to seek to dispense even 

 here with the historical vital force, and explain 

 everything by the great natural laws of the 

 cosmos. 



It was in this frame of mind that he received 

 Darwin's book. Can it be in the least surprising 

 that it " profoundly moved" him. It opened out 

 to him the whole way, just as he desired it. 

 Muller's third thesis, the immutability of species, 

 broke down. But what did it matter? It was 

 now possible for the first time to construct a 

 philosophical zoology and botany in Muller's sense, 

 without any vital force and without God. 



At the same time this rapid and impulsive 

 acceptance of Darwin's theory was not merely a 

 decisive moment in Haeckel's intellectual develop- 

 ment ; it was bound to be, even externally, a most 

 important step in his career. The theistic con- 

 troversy was forced on his attention. It passed 

 out of the province of his inmost life, that had 

 hitherto only been discussed in conversation with 

 intimate friends, into the professional work of his 

 most serious and public occupation into zoology, 

 into the radiolaria at which he had been working 

 for years. 



We must realise clearly what it must have 

 meant at that time for a young zoologist, who 



