Influence of Environment 243 



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 con- 

 stitution. 



Dominants and Recessives Remain Pure. A still more inti- 

 mate union takes place when the dominant and recessive char- 

 acters 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 get a clean separation of these characters in the next 

 generation ; neither the dominant nor the recessive character has 

 been at all modified by its mostantimate 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 Davenport and Castle (Figs. 86 and 87) ? 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 subsequent 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 exceptionally. 



