XVI] Practical Application 303 



Sociological Application. 



It may be anticipated that a general recognition of 

 the chief results of Mendelian analysis will brine about a 

 profound change in man's conceptions of his own nature 

 and in his outlook on the world. Many have in all ages 

 held the belief that our powers and characteristics are 

 directly dependent on physical composition ; but when it 

 becomes known that the dependence is so close that the 

 hereditary descent of certain attributes can be proved to 

 follow definite predicable formulae, these ideas acquire a 

 solidity they never possessed before, and it is likely that 

 the science of sociology will pass into a new phase. The 

 evidence at our disposal already proves that in many simple 

 cases of defects and abnormalities the descent is of this 

 definite order, and it is scarcely doubtful that future search 

 will reveal comparable examples in abundance. As regards 

 more complex phenomena of human inheritance, the descent 

 of characters involving the coincidence of several factors, 

 and effects due to interference between factors, a complete 

 analysis may be unattainable ; but even in some of these 

 more obscure examples a close scrutiny will probably discover 

 positive traces of regularity in descent of such a kind as to 

 indicate in them also that the bodily or mental characteristic 

 considered is a consequence of definite factorial composition. 

 It is not in dispute that the appearance or non-appearance 

 of a characteristic may be in part decided by environmental 

 influences. Opportunity given may decide that a character 

 manifests itself which without opportunity must have lain 

 dormant. The question of opportunity and of the degree 

 to which the conditions of life are operative in controlling 

 or developing characters will some day demand attention, 

 but in order to answer such questions successfully it is the 

 first necessity that a knowledge of the genetic behaviour of 

 the factors should be obtained. They are the fundamental 

 elements, and the consequences of environmental inter- 

 ferences are subordinate to them. The previous attempts, 

 experimental and statistical, to determine the results of 

 changed conditions have led to quite inconclusive results 

 because no pains were taken to ascertain that the material 

 subjected to these various influences was genetically similar. 



