FROM GENERATION TO GENERATION: 

 A PRELUDE TO THE STUDY OF HEREDITY. 



HEREDITY -is one of the fundamental laws underlying 

 the grand scheme of evolution ; and without the former, 

 the latter would lose all its significance and force, for by 

 its action the development and perpetuation of species is 

 maintained amid incessant variation, and all organised 

 beings tend to repeat themselves in their descendants. 

 As Ribot says : " Heredity and evolution are the two 

 necessary factors of every stable modification in the 

 domain of life. Suppose evolution without heredity, and 

 every change becomes transitory, every modification what- 

 ever, whether of good or bad, useful or hurtful, disappears 

 with the individual. . . . Suppose heredity without 

 evolution, and there is nothing but the monotonous 

 conservation of the same types, fixed once for all. Phy- 

 siological characters and instincts, intellectual and moral 

 faculties, are preserved and transmitted without modifica- 

 tion. . . . On the other hand, suppose both evolution 

 and heredity, and then life and variation become possible. 

 Evolution produces physiological and psychological modi- 

 fications, habit fixes these in the individual, heredity fixes 

 them in the race." Considered ideally, heredity would 

 be a simple question of like begetting its like, but this 

 is not so, as vital phenomena are not characterised by 

 such rigorous exactitude, the modifications of their exist- 

 ence tending to become more and more complex as we 

 ascend from the vegetable to the animal world, up to man 

 himself. 



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