WEISMANN'S ESSAYS UPON HEREDITY. 17 



family that mathematical power, can be transmitted from 

 generation to generation, but this teaches us nothing as to 

 the origin of such talents. In both families the high-water 

 mark of talent lies, not at the end of the series of genera- 

 tions, as it should do if the results of practice are trans- 

 mitted, but in the middle. Again, talents frequently appear 

 in some single member of a family which has not been 

 previously distinguished. Gauss was not the son of a 

 mathematician ; Handel's father was a surgeon, of whose 

 musical powers nothing is known ; Titian was the son and 

 also the nephew of a lawyer, while he and his brother, 

 Francesco Vecellio, were the first painters in a family which 

 produced a succession of seven other artists with diminishing 

 talents." 



We may sum up Professor Weismann's theory of 

 heredity in his own words : 



" I believe that heredity depends upon the fact that a small 

 portion of the effective substance of the germ, the germ- 

 plasm, remains unchanged during the development of the 

 ovum into an organism, and that this part of the germ- 

 plasm serves as a foundation from which the germ-cells of 

 the new organism are produced. There is, therefore, con- 

 tinuity of the germ-plasm from one generation to another. 

 . . . Hence it follows that the transmission of acquired 

 characters is an impossibility, for if the germ-plasm is not 

 formed anew in each individual, but is derived from that 

 which preceded it, its structure, and above all its molecular 

 constitution, cannot depend upon the individual in which it 

 happens to occur, but such an individual only forms, as it 

 were, the nutritive soil at the expense of which the germ- 

 plasm grows, while the latter possessed its characteristic 

 structure from the beginning viz., before the commence- 

 ment of growth. 



" But the tendencies of heredity, of which the germ-plasm 

 is the bearer, depend upon this very molecular structure, 



C 



