526 THE CHANGING WORLD 



Germplasm Theory of Weismann 



August Weismann (1834-1914), who was an ardent supporter of 

 Darwin, went straight at the heart of another difficulty, which not 

 only Darwin himself but also Lamarck had encountered, namely, 

 the problem of the manner in which inheritance takes place. 



A critical examination of available facts convinced Weismann that 

 only inborn characteristics are handed on from generation to genera- 

 tion, and that peculiarities picked up by parents during their lifetime 

 come to an end with the death of the individual. This led to the 

 formulation of the Germplasm Theory, namely, that the germ cells 

 from which the individuals arise, and which are the bearers of the 

 hereditary possibilities, are quite different from the innumerable 

 transitory cells that make up the rest of the body. According to 

 Weismann's theory, germinal material forms a continuous chain, 

 from which in successive generations individual organisms tempora- 

 rily develop. The germinal material, although it is subject to death 

 with the mortal body of the organism, is potentially immortal, because 

 in the process of reproduction it may continue from generation to 

 generation. 



This conception led Weismann to question the possibility of the 

 transmission of bodily acquisitions from one generation to another, 

 since the avenue of transmission is by way of the germinal stream and 

 not, as popularly supposed, from one body to another. The body is 

 simply the visible expression of the germinal characters handed on 

 from its ancestry, and for which it serves only as a temporary carrier. 

 The body of the individual does not produce the germ cells, as 

 Darwin's hypothesis of pangenesis assumed, but the germ cells produce 

 the body. It must be admitted that Weismann did a thorough job 

 in discrediting the supposed inheritance of acquired characters, 

 for today biologists are quite generally agreed that such inheritance 

 does not occur, or if it does, only to an insignificant extent. The 

 court of last resort for those who are unconvinced is appeal to further 

 facts, to be obtained by decisive experimentation. The value of 

 Weismann's speculative thought was largely due to the fact that it 

 stimulated further research and discovery. 



The whole course of evolution thus finally resolves itself into what 

 occurs in the unseen germplasm, as opposed to what takes place in the 

 visible parts of the body. Selection of variations of any sort is of 

 importance only when those bodily characters are recognized as 



