334 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 



the most conclusive demonstration that the hereditary character- 

 istics of the transplanted ova are in no wise changed by the foster 

 mother. They removed the ovary from a pure black guinea-pig and 

 put it in the place of the ovary of a pure white animal. After recover- 

 ing from the operation this white female with the "black" ovary was 

 bred to a pure white male. Three litters of offspring from these 

 parents were all pure black. Although both parents were pure white 

 all the offspring of the Fi generation were black because they came 

 from "black" eggs and black is dominant over white. The fact that 

 these "black" eggs developed in the body of a white female did not in 

 the least change their hereditary constitution. 



Dominants and recessives remain pure. -A still more intimate 

 union takes place when the dominant and recessive characters come 

 together in any zygote. These characters, or rather the factors which 

 determine them, may be intimately associated in every cell of the 

 organism throughout an entire generation and yet we may get a clean 

 separation of these characters in the next generation; in many cases 

 neither the dominant nor the recessive character has been at all modi- 

 fied by its most intimate association with the other. 



Climatic effects not inherited. A striking instance of the purely 

 temporary effect of the environment and of the long persistence of 

 hereditary constitution amidst new environmental conditions, which 

 have greatly changed the appearance of the developed organisms, is 

 found in the case of alpine plants. Nageli says that such plants, which 

 have preserved the characters of high mountain plants since the ice 

 age, lose these characters perfectly during their first summer in the 

 lowlands. 



Summary. If acquired characters were really inherited we should 

 expect to find many positive evidences of this instead of a few sporadic 

 and doubtful cases. In particular why do we not find in plant or 

 animal grafting that the influence of the stock changes the hereditary 

 potencies of the graft ? Why do we not find that transplanted ovaries 

 show the influence of the foster mother as Guthrie supposed a thing 

 which has been disproved by Castle ? Why do dominant and recessive 

 characters remain pure, even after their intimate union in a hybrid, so 

 that pure dominants and pure recessives may be obtained in subse- 

 quent generations from this mixture ? Why does every child have to 

 learn anew what his parents learned so laboriously before him ? Even 

 the strongest defenders of the inheritance of acquired characters are 

 constrained to admit that it occurs only sporadically and excep- 

 tionally. 



