1 1 THE AMERICAN NATURALIST [Vol. LV 



To determine whether the reappearance of the defect 

 was due merely to the passing on of antibodies or kindred 

 substances from the blood stream of the mother, or to 

 true inheritance, we mated defective-eyed males to nor- 

 mal females from strains of rabbits unrelated to our 

 defective-eyed stock. The first generations produced in 

 this way were invariably normal-eyed, but w^hen females 

 of this generation were mated to defective-eyed males 

 again, we secured defective-eyed young after the manner 

 of an extracted Mendelian recessive. It is obvious that 

 in such cases the abnormality could only have been con- 

 veyed through the germ-cells of the male, and that it is, 

 therefore, an example of true inheritance. Subsequent 

 matings have showTi that these young transmit the eye- 

 anomalies as effectively as do individuals of the original 

 lines. A new strain of defective-eyed young, established 

 about the time our original paper went to press, is also 

 flourishing and, as regards transmission of the defect, 

 seems to differ in no way from the earlier stock. 



But now^, let us inquire as to where all this leads. 

 Without entering into a discussion of just what, sero- 

 logically, is taking place in the body or in the germ of 

 fetuses borne by the lens-treated mothers, the point I 

 wish to emphasize is that a certain specific effect has 

 been produced ; and, what is of greater moment, once the 

 condition is established it may be not merely transmitted, 

 but inherited. Whether the lens of the uterine young is 

 first changed and then in turn induces a change in the 

 lens-producing antecedents in the germ-cells of these 

 young, or whether the specific antibody simultaneously 

 affects the eyes and the germ-cells of the young is not 

 clear. In any event it is evident that there is some con- 

 stitutional identity between the substance of the mature 

 organ in question and the material antecedents of such 

 an organ as it exists in the germ. 



Biologically considered, the most significant fact is 

 that specific antibodies can induce specific modifications 

 in the germ-cell. Whether these antibodies are trans- 



