THE DUALITY OP INHERITANCE 



inheritance. In all cases alike comnaunity of 

 descent is the basis of resemblances which can 

 be ascribed to heredity, whether direct or col- 

 lateral. Mother and child, no less than uncle 

 and nephew, resemble each other because they 

 have received a common inheritance from a 

 common ancestor. 



Three biological facts of fundamental im- 

 portance to a right understanding of heredity 

 were known imperfectly or not at all in the 

 time of Darwin and Mendel. These are (1) 

 the fertilization of the egg, (2) the maturation 

 of the egg, which must precede its fertilization, 

 and (3) the non-inheritance of " acquired " 

 characters. These we may consider in order. 



Every new organism is derived from a pre- 

 existing organism, so far as our present ex- 

 perience goes. It may not have been so al- 

 ways. Indeed, on the evolution theory, we 

 must suppose that living matter originally 

 arose from lifeless, inorganic matter. But if 

 it did, this may have occurred, and probably 

 did occur, under physical conditions quite 

 different from those now existing. At the 

 present time the most exhaustive researches 



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