178 THE BREEDING OF ANIMALS 



do not confirm those of Nathusius and Holdefleiss. Wal- 

 ther's investigations included not only color but also 

 size, form and glossiness. His conclusions were that 

 the paternal parent has no influence on the size, shape 

 and glossiness of the eggs. His results on the color of 

 eggs are not conclusive but tend to discredit the theory 

 of xenia in fowls. From all the evidence available, it 

 would seem that the possibility of xenia in fowls is not 

 satisfactorily determined, and further investigation is 

 needed to settle this supposed influence of the male bird 

 on the color of eggs. 



OBJECTIONS TO THE THEORY THAT ACQUIRED CHARACTERS 

 ARE TRANSMITTED 



The trend of opinion of modern biologists has been 

 further and further away from the belief in the possibility 

 of the inheritance of acquired characters. As our knowl- 

 edge of cellular biology has increased and we have been 

 able to study the mechanical processes which are concerned 

 in reproduction and heredity, it has become more and 

 more apparent that Weismann's view of the essential 

 separateness of the soma-cells and germ-cells is sub- 

 stantially correct. 



165. No mechanism for the inheritance of acquired 

 characters. There is no mechanism by means of which 

 somatic modifications may impress themselves funda- 

 mentally upon the germ-plasm. In fact, the develop- 

 ment of the soma-cells is made possible by determiners 

 in the germ-cell. The very fact that the soma-cells 

 have been able to respond to external influences and 

 develop in a direction somewhat different from the average 

 of the species is sufficient evidence that the determiners 



