468 GROWTH OF BIOLOGY IN THE NINETEENTH CENTURY. 



world of organisms. In 1859 Charles Darwin published his epoch- 

 makino- work upon the orig-in of species, a work distinguished for the 

 collection and sifting of a great and previously little-notici'd mass of 

 facts, and by being crammed with important new points of view. In 

 particular much light was thrown by Darwin upon the relations of 

 organisms to one another and to environing nature, ji sul)i(>ct which 

 had prc\ iously l)cen neglected and even now is little understood, 

 notwithstanding the ])artial insight into it which that great genius has 

 ati'ordcd. 



More fortunate than his forerunner, whose merit was only tirst 

 recognized l)y posterity. Darwin saw his doctrine fall upon ])etter pre- 

 pared soil, so that it j)roduccd a scientific moviMuent sustained by 

 enthusiasm and adopting his luimc. Darwinism. He had the good luck 

 to be supi)lcmcnted by a powerful advocate, IIaeck«d, who in knowl- 

 edge^ of anatomy and of the history of <le\ ('lo])ment far sui'passed him. 

 Men now ))elieved that the secret of how new organic species arise 

 was at last out; that the riddle of the "true causes of forms" had been 

 guessed, and that the theory of selection furnished the elucidation of 

 the theory of descent. ''Struggle for existence," '"'survival of the 

 tittest," "natural selection," were the fornuda' 1)V which the organic 

 empire was to be laid open. Adherents and (opponents to the nmv 

 doctrine appeared. Hither and thither waged the battle with a 

 vehemence which scientific hypotheses seldom inspire. Darwinists, 

 UltradarW'inists, Antidarwinists, Neodarwinists, Haeckelians, and 

 Weismannists mingled in the fray. Weismann, going beyond Dar- 

 win, pu))lished The Omnipotence of Natural Selection; Herbert 

 Spencer hurled at him with The Inadequac}' of Natural Selection. 



This sort of thing is comprehensible in politics, but how shall we 

 explain such a remarkable turmoil about a scicHitific question? It 

 seems to me that not the least of the reasons was that the formulae of 

 explanation, "struggle for existence," "survival of the fittest," 

 "selection," are very vague expressions, which only gain scientific 

 value b}^ the mode in which they are applied in the concrete cas(\ 

 Why has the term "struggle for existence" not been brought down to 

 application? It has become a standing and favorite form of words in 

 writings upon national economy' and politics: and there it is excusable. 

 But it l)egins to be less so when, at the Darwinian ilood tide, Du Prel 

 would use it as a formula to explain the motions of the heavenly 

 bodies. With too general terms single cases can not be explained, or 

 a mere shadow of an explanation is given, while the true causal connec- 

 tion remains as much in the dark as before. Now, the problem of sci- 

 entific research is to make out the precise cause of an observed effect, 

 or, more corrects, since nothing happens from a single cause, its dif- 

 ferent causes. 



But surely the origin of the organic world by natural causes is an 

 extraordinarily intricate and difficult pro1)lem. It is as little to be 



