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In seeking to account for these metamorphoses in trans- 

 mission, occurring as they do, not only between generation 

 and generation, but also frequently in the same individual, 

 various physiologists have given as diverse- opinions ; some 

 regarding them simply as exceptions to the law of heredity ; 

 others, as the result of a law of spontaneity, acting reci- 

 procally with heredity ; others, again, as the result of both 

 parents presenting the same characteristics, when heredity 

 may acquire such power as to destroy itself. In following 

 out my argument, however, I contend that these metamor- 

 phoses are simply the natural phenomena of the law of 

 variability to which every individual is subject, and which 

 is the fundamental element in his individuality. Heredity, 

 we have seen, is the ideal, but unattainable law ; for Nature 

 preserves the type or species not by simply reproducing 

 the parents in the children in a monotonous succession, 

 but by varying each individual within certain limits, so that 

 no two individuals who have ever existed have been precisely 

 alike. This fact, to which I have already alluded more 

 than once, is to my mind a conclusive proof that these 

 transformations in transmission are the result of the law of 

 variability interacting with that of heredity ; for this varia- 

 bility of individuals extends to their whole nature phy- 

 siological and psychological; and if so, why not also to 

 those morbid predispositions which we include under the 

 term pathological, since all are inherited in various degrees, 

 varying with the individual. For example, let us suppose a 

 man of nervous temperament marrying with a woman 

 who has suffered from hysteria ; their offspring will to some 

 extent resemble one or both physically, mentally, and 

 morally ; but deeper down in the constitutions which they 

 have inherited dwell potentialities capable of producing 



