MODERNBIOLOGY 5 79 



of fact, Roux also has points of contact with Weismann, whose theory 

 of the continuity of the germinal plasm he embraces; he consequently re- 

 jects the theory of the heredity of acquired characters. He resembles Weis- 

 mann, too, in the fact that he likes discussing hypothetical entities of life, 

 whereof he enumerates a whole series, which, however, it is not worth 

 while dilating upon here. For these very reasons he was on bad terms with 

 O. Hertwig, who, as we have seen, entertained quite different views, just 

 as, on the other hand, he was at variance with Haeckel and other original 

 Darwinists on account of his mechanical theory of evolution. 



Creation of evolutional mechanics 

 The theoretical speculations upon descent are, however, a less essential side 

 of Roux's research work. He will mostly be remembered as the creator of 

 experimental embryology; whether the theories that he based upon his ex- 

 periments are eventually accepted or rejected, there is no doubt at any rate 

 about the fact that he created a special method of research, which has proved 

 productive and was largely employed by his contemporaries. But he also 

 exercised considerable influence upon the theoretical conception of biology 

 itself; he has directed research to a series of problems which many, following 

 his precedent, have taken up for treatment and which have largely guided 

 modern biological research. He himself defined as the aim of the new science 

 that he desired to found the elucidation of the "true causes of formation" 

 to which all living creatures and every single individual must attribute 

 their origin — a subject in which the earlier "descriptive natural science," 

 to his mind, failed to show any interest. These causes of "form-building 

 forces," whereby the individual organism receives step by step the form that 

 characterizes it, must, in his opinion, be studied primarily by way of ex- 

 periment; if a process of development is altered by different kinds of inter- 

 ference, it is possible by combining the results to discover the cause of the 

 process; thus is created a "causal-analytical form of research," such as chem- 

 istry and physics had already realized in many instances. 



Natural selection ivithin the organism 

 As previously mentioned, Roux began his activities with a theory of func- 

 tional adaptation produced by means of natural selection within the organ- 

 ism. This theory he sought to apply to the organs of various vertebrate 

 animals; he measured a large number of muscles in man and tried to deter- 

 mine to what extent their dimensions are dependent upon one another; he 

 studied the caudal fin of the dolphin from a mechanical point of view and 

 sought to determine the lines and curves in which these tissues are arranged 

 in order mechanically to sustain the function of the whole. After a short 

 time, however, he went over entirely to embryology, and in this field pro- 

 pounded the question to what extent and how far back in evolution certain or- 

 gans and tissues are predestined to assume their prospective form and function. 



