Mutations and Evolution. 
217 
CHAPTER VIII. 
Limitations of the Cell Theory , 1 
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 are 
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 Linnean Society, February 5th, 1920. 
