76 Mutations and Evolution. 



CHAPTER VIII. 

 LIMITATIONS OF THE CELL THEORY.' 



The work of the present century in experimental breeding and 

 cytology has led to many new points of view and new lines of 

 approach to old problems. It therefore seems desirable to examine 

 our present bearings from the point of view expressed in previous 

 chapters. That the experimental method of attack upon the 

 problems of variation and heredity, as well as those of embryology, 

 is sound and of the utmost value cannot be gainsaid. On the other 

 hand, it does not follow that the older conceptions of evolution, 

 natural selection, and the inheritance of acquired characters aie 

 necessarily unsound or, if adhered to, subversive of the modern 

 experimental results. We wish to show (1), that the experimentalist 

 point of view resulting from the work in mutation and Mendelism 

 is frankly antagonistic to the views of many palaeontologists, 

 anatomists and others who deal with the non-experimental data of 

 evolution involving orthogenesis and the inheritance of acquired 

 characters (2), that while these two factors bear entirely different 

 relations to evolutionary changes, both are necessary to account 

 for evolution as it has taken place. 



It may be said that the divergence between the geneticist point 

 of view and that of the biologist who relies upon the historical back- 

 ground of evolution for his interpretation of evolutionary factors 

 has long been manifest; and that is true. Yet we venture to think 

 that no one has clearly visualized or set forth the fundamental 

 character of this antagonism in relation to the structure of the 

 organism. Moreover, those who have recognised the opposition 

 between the principles of germinal variation and inheritance of 

 acquired characters in evolution have usually endeavoured to solve 

 the difficulty by denying or ignoring one principal and affirming the 

 other. Rather, we think it necessary to harmonize these two 

 conflicting views into a more complete and balanced conception of 

 the evolutionary process. 



We propose, then, to show that higher organisms exhibit two 

 sharply contrasted types of characters which differ fundamentally, 

 (1) in their manner of origin, (2) in their relation to the structure of 

 the the organism, (3) in their relations to such phenomena 



1 The following chapters are chiefly based on a discussion "On the 

 Existence of two fundamentally different types of characters in Organisms," 

 which took place at the Ltnnean Society, February 5th, 1920. 



