18 



Problems, Concepts and Their History 



trine. Its supplanting had therefore to wait 

 until a new period demanded a different kind 

 of thought, and until Wilhelm Roux could 

 succeed where Leuckart and Bergmann and 

 His had apparently failed. 



The attempts at mechanical explanations 

 of development begun by His and the others 

 in the 1870's were surely an outgrowth of 

 the whole philosophy of materialism that 

 pervaded the thinking of the 19th century. 

 But the 19th century was also a strongly 

 romantic century in many ways, perhaps 

 again specifically in reaction against mate- 

 rialism. It is a curious paradox that the 

 Haeckelian doctrines, steeped in romantic 

 idealism, emanated from the impersonal and 

 objective doctrines of Darwin. But they did, 

 and in doing so, floiu-ished with sufficient 

 strength to repress the mechanical theories 

 of development really so much more com- 

 patible with the doctrines of evolution; and 

 it is ironical that therefore the success of 

 the new embryological theories had to await 

 a waning of interest in Darwinism. 



It must be admitted, however, that al- 

 though evolution had delayed the new move- 

 ment in one way, it is also true, in another, 

 that it fostered it. The new interest in the 

 new embryology came again from a new at- 

 tack on the problem of epigenesis versus 

 preformation, and this derived its origin 

 from the absorption of the evolution doctrine 

 into everyday thinking. The process of evo- 

 lution implies epigenesis, in that change is 

 the essence of both, and a gradual process 

 from step to step. A generation habituated 

 to thinking about change building on change 

 in evolution could more easily than its 

 fathers accept the concept of epigenesis with 

 its causal connotations. Embryologists have 

 been familiar with chain reactions for cen- 

 turies; the significance of progressive dif- 

 ferentiation in ontogeny had been made ex- 

 plicit in the modern sense by Leuckart and 

 Bergmann, and through His, who though 

 his "organbildende Keimbezirke" are usually 

 accredited for heralding neo-preformation, 

 yet inferred the causal relationships implicit 

 in neo-epigenesis (1874, p. 2): 



Die Entwicklungsgeschichte ist ihrem Wesen 

 nach eine physiologische Wissenschaft, sie hat den 

 Aufbau jeder einzelnen Form aus dem Ei nach den 

 verschiedenen Phasen nicht allein zu beschreiben, 

 sondem derart abzuleiten, dass jede Entwicklungs- 

 stufe mit alien ihren Besonderheiten als noth- 

 wendige Folge der unmittelbar vorangegangenen 

 erscheint. 



Roux himself, who was a student of 

 Haeckel's, and felt himself his disciple, very 



definitely acted as intermediator between 

 Darwinism and the new causal analytical 

 embryology. His "Kampf der Theile im Or- 

 ganismen," though written before his great 

 concentration of interest on embryological 

 problems, was consummately important in 

 this respect. By striking an analogy between 

 the struggle for existence among organisms 

 on the one hand, and that between the parts 

 of an organism on the other, Roux pointed 

 up for the first time in a new way the pos- 

 sible significance for differentiation of inter- 

 relationships between tissues, and suggested 

 the possibility already in that communica- 

 tion of the "Hervorbildung des chemisch 

 und morphologisch Differenzirteren aus dem 

 Einfacheren ohne differenzirende aussere 

 Einwirkungen," as opposed to the conditions 

 where "andere Gewebe . . . secundar durch 

 Einwirkung seitens der ersteren aus dem 

 embryonalen Blastem differenzirt werden" 

 riSSl; cited from Roux, 1895a, I, 332-333). 

 But are not these clearly Haeckel's innere 

 and aussere Bildungstriebe — ^words and con- 

 cepts borrowed by him deliberately from 

 Goethe? And Haeckel, for all his faults, was 

 infected by Goethe with an enthusiasm for 

 the dynamic wholeness of the organism and 

 its environment, which he passed on to Roux 

 who made vise of it as Haeckel never could. 

 Spemann was to be moved by it too. He 

 mentioned in his autobiography having 

 known Martin Donndorf who had seen Ecker- 

 mann, and commented that "man wird 

 nicht mehr leicht jemand begegnen, der in 

 Augen geblickt hat, welche Goethe gesehen 

 haben" (['43], p. 86). His own intellectual 

 distance from Goethe was, like Roux', dimin- 

 ished by the intermediacy of Haeckel: 



Im Lager fiel mir das Buch von Wilhelm Preyer 

 iiber die Seele des Kindes in die Hand; mit schlech- 

 tem Gewissen, wie ein Schuliunge mit einem Buch 

 unter der Bank, sass ich damit in einer dunklen 

 Ecke. Das kam aus der Gegend von Ernst Haeckel, 

 der so manchen jungen Mann meiner und der vor- 

 hergehenden Generation zur Biologie gefiihrt hatte. 

 Dort begegnete ich auch zum erstenmal. soviel ich 

 mich erinnere. dem Begriff der Biologie als einer 

 umfassenden Wissenschaft vom Leben, mit all ihren 

 aufwiihlenden Lehren iiber seine letzte Tiefe (ibid., 

 p. 116). 



But if Roux began his work against the 

 natural philosophical background of Haeckel, 

 from whom he also inherited his predilection 

 for setting up his concepts in a strongly 

 theoretical framework, he was later to grow 

 far beyond Haeckel's romanticism. Haeckel's 

 own strong predilection for monism may 

 have exerted its influence in this respect. But 

 Roux had studied also with Goette. Particu- 



