214 



The Journal of Heredity 



calculation. Some of these difficulties 

 have been leveled, others are yet to 

 be overcome. 



One must realize that each gene has 

 many effects on the organism, some 

 of which are not easily discoverable. 

 The fact that a gene is usually ticketed 

 with a name indicative of its most 

 obvious effect on a particular charac- 

 ter, should not mislead us in this regard. 

 Then, too, one must remember that 

 many genes affect each organic char- 

 acter; and that similar characters, 

 characters apparently identical, do not 

 necessarily owe their qualities to the 

 same combination of genes. And, 

 finally, it does not follow from any of 

 the above relations, what will be the 

 result of gene interaction. The action 

 of two or more genes may be necessary 

 to bring about a visible or measurable 

 result, though these genes may be 

 carried along separately generation 

 after generation. The full logic of this 

 fact tears down the veil from many an 



obscure result; since the difficulty of 

 appreciating the results of selection 

 has been due to the failure to realize 

 how many modifying genes may be 

 carried along which have no chance to 

 produce a measurable effect unless a 

 certain basic gene complex necessary 

 for particular organic expression is also 

 present. 



This short sketch will show, I hope, 

 that in the twenty-one years of experi- 

 mental genetics real progress has been 

 made. To be sure, this resume has 

 been a leaping from crag to crag. No 

 more was possible within the editorial 

 limits here allotted. But if one recalls 

 the scorn of fifty years ago should a 

 daring seer have predicted such a 

 triumph for quantitative mechanical 

 analysis in a subject so overstrewn 

 with variable factors, he in turn will 

 scorn the Freudian over-compensation 

 of today's critic who makes the taunt 

 that it shall go no further. 



A Clearer Understanding of Applied Eugenics Necessary 



"We believe that a clear view of the 

 underlying biologic facts will greatly 

 help us to a more comprehensive under- 

 standing of the surface problems of an 

 economic and political nature." 



"If we can do something im.mediately 

 and directly to advance the health and 

 vigor of the American people; if we can 

 set in motion influences which will 

 certainly improve both the quantity 

 and quality of the next generation; if 

 we can do something to lessen the flood 

 of inferior immigrant stock, which 



deteriorates our national worth — if we 

 can do only a little to realize some of 

 the hopes of better things — then we 

 will also have done much to improve 

 our industrial situation and to better 

 our social and economic status. Our 

 social questions are not going to be 

 finally settled by a generation that 

 refuses to study and know the laws 

 of human heredity, and which closes its 

 eyes to the scientific principles of race 

 betterment and national uplift." — 

 Wm. S. Sadler, M.D. 



