

o24 THE HK<;iNNIN(;S OF CAUSAL MOKPIIOUHi Y 



chemical changes, or are correlative with such, and that, 

 since the germ-cells stand in close metabolic relations with 

 the soma, these chemical changes may soak through to the 

 germ-cells and so modify them that a predisposition will 

 appear in the descendants towards similar form-changes. 1 

 From this point of view the problem of transmission might 

 be merged in the broader problem of the production of form 

 through chemical processes the central problem of all 

 development. 



Inherited characters develop by an automatic process of 

 self-differentiation, and the separate parts of the embryo 

 show during this first period a surprising functional inde- 

 pendence of one another. But this state of things changes 

 progressively as the second period is reached, until finally 

 all form-production and maintenance and all correlation 

 depend upon functioning. It is in the first period of auto- 

 matic development through internal " determining " factors 

 that the "developmental" functions in the strict sense, 

 e.g. automatic growth, division and self-differentiation, are 

 most clearly shown. In the second or "functional" period 

 the formative influence of function upon structure comes 

 into play, and development becomes largely a matter of 

 "functional adaptation" to functional requirements. 



All structure, according to Roux, is either functional or 

 non-functional. The former includes all structure that is 

 adapted to subserve some function. " Such ' functional 

 structures' are, for example, the composition of striated 

 muscle fibres out of fibrilhu and these out of muscle-prisms, 

 or again the length and thickness of the muscles, the static 

 structure of the bones, the composition of the stomach and 

 the blood-vessels out of longitudinal and circular fibres, tin- 

 external shape of the vertebral centra and of the cuneiform 

 bones of the foot" (p. 73, 1910). Indeed, as Cuvier had 

 already pointed out, practically every organ in the body 

 shows a functional structure which is accurately and minutely 

 adjusted to the function it is intended to perform. Thus, to 

 take some further examples, the arteries are admirably 

 adapted as regards six.e of lumen, elasticity of wall, direction 

 of branching, to conduct the blood to all parts of the body 



1 See, for the development of this idea, Oppel, in Roux-Oppel, 1910. 



