ROUX: "COMPLEX COMPONENTS 11 319 



upon the fundamental properties of living matter. The aim 

 of Entwicblungsmechanik is defined by Roux to be the 

 reduction of developmental events to the fewest and simplest 

 Wirkungsweisen, or causal processes. 1 Two classes of causal 

 processes may be distinguished, as "complex components" 

 and "simple components " of development. The latter are 

 directly explicable by the laws of physics and chemistry ; 

 the former, while in essence physico-chemical, are yet so 

 very complicated that they cannot at present be reduced to 

 physico-chemical terms. The ultimate aim of Entwick- 

 lungsmechanik is to reduce development to its " simple 

 components," but its main task at the present day and for 

 many years to come is the analysis of development into its 

 " complex components." 



These complex components must be accepted as having 

 much of the validity of physical and chemical laws. They 

 are mysterious in the sense that they cannot yet be explained 

 mechanistically, but they are constant in their action, and 

 under the same conditions produce always the same effect 

 hence they may be made the subject of strictly scientific 

 study. They represent biological generalisations, in their 

 way of equal validity with the generalisations of physics and 

 chemistry. 



The principal " complex components " which Roux 

 recognises are somewhat as follows : First come the 

 elementary cell-functions of assimilation and dissimilation, 

 growth, reproduction and heredity, movement and self- 

 division (as a special co-ordination of cell-movements). 

 Then at a somewhat higher level, self-differentiation, and the 

 trophic reaction to functional stimuli. Components of even 

 greater complexity may also be distinguished, as, for instance, 

 the biogenetic law. The various tropisms exhibited in 

 development may be regarded as "directive" complex 

 components. There must be added, not as being itself 

 a component, but rather as a mode or peculiar property of all 

 functioning, the omnipresent faculty of self-regulation. 



It will be noticed that Roux's "complex components" are 



The exact quantitative formulation of a Wirkungsivcise constitutes 

 a law. The word itself is perhaps most conveniently rendered as 

 " causal process." 



