LECTURE VI PART II 



A NOTE ON THE VIEWS OF G ALTON AND WEISMANN ON 

 INHERITANCE 



Two of the most prominent writers on inheritance, Weismann 

 and Galton, base their views of variation on the assumption that 

 at each remote generation, the ancestors of a modern organism 

 were innumerable, although a little reflection will show that this 

 assumption is quite untenable. 



Weismann, in his earlier writings at least, finds the " cause of 

 variation " in the recombination, by sexual reproduction, of the 

 effects of the diversified influences which acted upon the innumer- 

 able protozoic ancestors of each modern metazoon ; but this 

 opinion deserves little consideration, as a contribution to our 

 knowledge of inheritance, if we can prove that these protozoic 

 ancestors must have been very few, and if we can also prove that, 

 if these few were ancestors of any modern metazoon, they must 

 have been the common ancestors of all the modern metazoa. 



Galton's view of the diversity among individuals is much like 

 Weismann's. He says : " It is not possible that more than one- 

 half of the varieties and number of the parental elements, latent 

 or potential, can on the average subsist in the offspring. For if 

 every variety contributed its representatives, each child would on 

 the average contain, actually or potentially, twice the variety and 

 twice the number of elements, whatever they may be, that were 

 possessed at the same stage of its life by either of its parents, 

 four times as many as any of its grandparents, 1024 times as 

 many as any of its ancestors of the tenth degree, and so on." 



As he holds that each offspring must therefore get rid, in 

 some way, of half the variety transmitted from its ancestors, he 

 finds an explanation of the diversity between individuals in the 

 diversity of the retained halves of their variety. 



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