EXPERIMENTAL MORPHOGENESIS 57 



we owe another set of analytical considerations about 

 ontogeny. Newport, as early as 1850, and in later years 

 Pflliger and Rauber, carried out experiments on the eggs of 

 the frog, which may truly be called anticipatory of what 

 was to follow. But it was Wilhelm Roux, 1 now professor 

 of anatomy at Halle, who entered the field with a thoroughly 

 elaborated programme, who knew not only how to state the 

 problem analytically, but also how to attack it, fully 

 convinced of the importance of what he did. "Entwickelungs- 

 rnechanik," mechanics of development he called the " new 

 branch of anatomical science " of which he tried to lay the 

 foundations. 



I cannot let this occasion pass without emphasising in 

 the most decided manner how highly in my opinion 

 Koux's services to the systematic exploration of morpho- 

 genesis must be esteemed. I feel the more obliged to do 

 so, because later on I shall have to contradict not only 

 many of his positive statements but also most of his 

 theoretical views. He himself has lately given up much of 

 what he most strongly advocated only ten years ago. But 

 Eoux's place in the history of biological science can never 

 be altered, let science take what path it will. 



It is not the place here to develop the logic of 

 experiment ; least of all is it necessary in the country 

 of John Stuart Mill. All of you know that experiment, by 

 its method of isolating the single constituents of complicated 

 phenomena, is the principal aid in the discovery of so-called 

 causal relations. Let us try then to see what causal 



1 Gesammelte Abhandlungen, Leipzig, 1895. Most important theoretical 

 papers: Zeitschr. Biolog. 21, 1885 ; Die Entwickelungsmechanik der Organis- 

 men, Wien, 1890 ; Vortrdge und Aufsatze iiber Entwickelungsmechanik, 

 Heft i., Leipzig, 1905. 



