242 Heredity and Environment 



No Inherited Influence of Stock on Graft. If specific changes 

 of environment produced specific changes in heredity we should 

 expect to find that where different plants or animals are grafted 

 together each would modify more or less the hereditary consti- 

 tution of the other. But this does not occur. Everybody knows 

 that when a branch of a particular kind of fruit tree is grafted 

 upon a tree of a different variety the quality of the fruit borne by 

 that branch is not altered by its close union with the new stock. 

 The same is true of all forms of animal grafts. Harrison cut in 

 two young tadpoles of two species of frog, Rcma sylvatica and 

 Rana palustris, and spliced the anterior half of one to the posterior 

 half of the other. These frogs and their tadpoles differ in color 

 as well as in other respects, R. sylvatica being more deeply pig- 

 mented than R. palustris. In the grafted tadpoles each half 

 preserved its own peculiarities even up to the adult condition 

 (Fig. 8 5 ). 



A still more striking case of the persistence of heredity in spite 

 of environmental changes is found in experiments in which the 

 ovaries are removed from one variety of animal and transplanted 

 to another variety. Guthrie made such transplantations in the case 

 of fowls and concluded that there was some influence of the fos- 

 ter mother upon the transplanted ovary, but Davenport, who re- 

 peated his experiments, was unable to confirm his results ; on the 

 contrary he frequently found that the engrafted ovary degenerated 

 and that the excised ovary regenerated. Finally Castle and 

 Phillips furnished the most conclusive demonstration that the 

 hereditary characteristics 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 recovery from the operation this 

 white female with the "black" ovary was bred to a pure white 

 male (Fig. 86). Three litters of offspring from these parents 

 were all black as shown in Figure 87. Although both parents 

 were pure white all the offspring of the F : generation were black 



