176 EVOLUTION AND GENETICS 



transplanted into a white female whose ovary had 

 been removed. After the transplanted ovary had 

 established itself, the white female was bred to a 

 pure white male. The offspring were black, although 

 the mother and the father were white. The eggs had 

 not been affected by their sojourn in the body of a 

 white individual. 



It is not as widely known as it should be that 

 most of the assumptions of the Lamarckians contra- 

 dict the fundamental principles of JNIendel's law of 

 heredity. Mendel's law of segregation states that 

 the hereditary elements received from the parents 

 separate in the germ-cells of the offspring without 

 having affected each other, and, hy implication, 

 without having been affected by the character of the 

 individual in which thev were contained. An ex- 

 ample will make this statement clearer. Suj^pose a 

 white mouse is bred to a wild gray mouse. The hy- 

 brid offspring will be gray. If two such hybrids are 

 bred together they give rise to gray and to white 

 offspring in the ratio of three grays to one white. 

 This ratio is understandable if in the hj^brids half 

 of the reproductive cells carry the element for gray 

 and half that for white. Thousands of instances of 

 this sort are known today. To reject the evidence 

 would be scientific suicide; to refuse to accept the 

 theorv would be to throw reason to the winds. Men- 

 del's j^ostulates concerning the clear separation of the 

 elements of heredity mean that the white-producing 



