274 COOK 



the variety of chemical compounds which might be found in the 

 soil of the same seed-bed. But no evidence of any constant 

 relation between any particular chemical and any particular 

 mutative character has been adduced. That any will be forth- 

 coming may well be doubted, in view of the fact that the same 

 or closely similar mutative characters often appear under very 

 different conditions of soil and climate, and very diverse muta- 

 tions under the same conditions. 



The diversity of the mutations among themselves shows that 

 it is not safe as yet to assert more than this general organic in- 

 stability ; detailed causes are not yet revealed. The necessity 

 of this caution is rendered still more obvious by the behavior of 

 neotopic mutations, those induced by changes of environmental 

 conditions. If in a given environment a plant mutated only in 

 one direction, we would still be far from knowing adequately 

 that the environment caused the mutation, but even when we 

 have reason to believe that a change of environment has induced 

 mutation we are forbidden to go farther, because of the very 

 great diversity of the mutations which the same change of envi- 

 ronment or the same history of selective inbreeding can induce. 



It has been shown in the discussion of neotopism that new 

 conditions may conduce to the appearance of abruptly discon- 

 tinuous mutative variations. The percentage of mutants is 

 notably larger in some regions than in others, but even this 

 does not compel us to believe that the conditions are the true 

 cause of the mutations, in any detailed sense. They are rather 

 to be thought of as merely the occasion of the change, by having 

 brought the coffee, the cotton or the Capsicum the sooner to the 

 point when it can no longer follow the hereditary road over 

 which the individuals must travel to attain the ancestral type of 

 adult form. 



The mutative individuals are not to be thought of as the evo- 

 lutionary pioneers of the species ; they represent rather those 

 who are falling out by the wayside. They may be classed to- 

 gether with normal new variations in the sense that they are 

 outside of the specific norm or average, but the)' have a dif- 

 ferent position with reference to the evolutionary route of the 

 species. They represent the criminals and cranks, but not the 



