188 INHERITANCE, FERTILITY, AND SEX IN PIGEONS. 



not the laboratories alone, but the laboratories reinforced and supplemented by 

 every method of research in the study of living organisms. 



There is no one highway to solution. We can not circumvent it by curves of 

 probability. The philosophy of chance is wholly superficial. The more we know 

 the less room there will be for chance. It is our business to eliminate chance by 

 tracing the history of the elements supposed to obey chance. 



In studies on evolution our material, first of all, must be selected with a view to 

 eliminating chance. We must work with pure species — that is, with wild species 

 rather than domestic mix-ups. Purity in species means that we can know some- 

 thing about our subject. Some wild species are mix-ups; they can not be our main 

 dependence. Their behavior must be judged by that of better known forms. 



Variation is not chance, and fluctuation is a thing to be studied. The more we 

 lump things and hide details the more we get lost in the wilderness of chance. 



