820 POPULAR SCIENCE MONTHLY. 



scientific concept; in Herbert Spencer's hands, it grew to be a 

 probable and rational theory, based upon a serious array of con- 

 firmatory facts, and fulfilling all the conditions of a sound work- 

 ing hypothesis. If the reader will turn once more to Mr. Spen- 

 cer's pronouncement, published seven years before The Origin of 

 Species, he will see that there Mr. Spencer has brought together 

 almost all the chief arguments which still weigh in favor of the the- 

 ory of descent and modification. Mr. Clodd has collected a large 

 number of passages from Mr. Spencer's early works especially 

 passages from scattered articles prior to the first public hint of 

 Darwin's idea which amply prove Mr. Spencer's claim to rank 

 as an entirely independent author of the doctrine of organic evo- 

 lution. The fact is, before Darwin's book appeared, the argument 

 from variation, the arguments from plants and animals under 

 domestication, the argument from embryology, the argument 

 from geographical distribution, the argument from distribution 

 in geological time, had all of them been brought forward, and 

 some of them had been treated with great skill and efi:ect, by Mr. 

 Spencer. Indeed, it was above all von Baer's law of embryologi- 

 cal development which led Mr. Spencer both to his first clear 

 conception of the method of biological evolution, and to his first 

 incomplete conception of evolution in general as fundamentally 

 a progress from the homogeneous to the heterogeneous. 



Why, then, if so many minds had already grasped the doc- 

 trine of descent with modification, did Darwin's immortal treatise 

 produce so immediate and noteworthy a mental revolution ? 

 Why did the world which turned a deaf ear to Lamarck, and 

 even to Spencer, listen gladly to Charles Darwin ? Clearly, 

 because Darwin had something new and important to add to the 

 concept ; and that " something new " was the theory of natural 

 selection. This was Darwin's real contribution to the world's 

 thought. He arrived at it at first as a stray apergu ; he followed 

 it up, with Darwinian patience, with astonishing wealth of knowl- 

 edge and instance, with single-hearted devotion to the particular 

 subject, through the whole of his life ; and he left it at the end as 

 nearly certain as such a thesis can ever be made by human intelli- 

 gence. The weak point in the hypothesis of organic evolution, 

 before Darwin, was the difficulty of understanding the nature and 

 cause of adaptation to the environment. That weak point, when 

 supplemented by theological preconception, made many or most 

 biologists hesitate to accept the nascent theory, in Lamarck's and 

 Spencer's presentment. It is true, minds like Lamarck's and 

 Spencer's could never for a moment, on the other hand, have 

 accepted the crude and unthinkable dogma of separate creation ; 

 but the mass of biologists, incapable of high philosophic reason- 

 ing, held their judgment suspended, and waited for some other 



