50 CONTROLLED NATURAL SELECTION 



geneous environment, then living matter would 

 assume an infinite number of different forms, 

 corresponding to the infinite number of the 

 diversities of its environment ; and each form 

 would be infinitely restricted (see Fig. 3). 

 Associated with this adaptation must be 

 structural alteration ; function and structure 

 are inseparable these are acquired char- 

 acters. 



Nevertheless, in spite of this power of adap- 

 tation, one cannot conceive a variation of a 

 species, whatever its nature, displacing another 

 species from its specific environment, which 

 it completely fills and perfectly fits ; to accom- 

 plish this, the variation would have to differ 

 from the parent in a great number of struc- 

 tures, be a great mutation and would have 

 at the same time to fit perfectly a new 

 environment, in fact more perfectly than the 

 former occupier, which itself is a perfect fit ; 

 can such a correlation come about through 

 Chance ? 



Change in Environment. Change in en- 

 vironment may be quantitative ; the specific 

 environment may increase, decrease, or dis- 

 appear entirely, in which case the species will 

 becomejcommon, rare, or extinct. The change 

 may be qualitative, and consist in the addi- 



