634 Studies in the Theory of Descent. 



IV. 



ON THE MECHANICAL CONCEPTION OF NATURE. 



INTRODUCTION. 



IN the first of the three preceding essays it was 

 attempted to solve the question whether the trans- 

 formations of a given complex of characters in a 

 certain systematic group could be completely ex- 

 plained by tbe sole aid of Darwinian principles. 

 It was attempted to trace the origin of the marking 

 and colouring of the Sphinx-caterpillars to indi- 

 vidual variability, to the influences of the environ- 

 ment, and to the laws of correlation acting within 

 the organism. These principles as applied to the 

 origin of a certain well-defined, although narrowly 

 restricted range of forms, were tested in order to 

 see whether they were alone sufficient to explain 

 the transformation of the forms. 



It appeared that this was certainly the case. 

 In all instances, or at least where the facts neces- 

 sary to obtain a complete insight were available, 

 the transformations could be traced to these 

 known factors ; there remained no inexplicable 

 residual phenomena, and we therefore had no 



