FACTS 195 



ticularly what has become of the living body itself, while 

 neglecting the environment or sum total B of the factors. 

 We even always keep the same denomination for the living 

 body after it has acted ; and this is the origin of a great 

 number of errors in reasoning, for we easily believe in the 

 identity of two objects bearing the same designation. 



The language we have so far used is exact : the living 

 body A, executing under circumstances B the operation 

 (A x B) becomes AI. But so long as A remains living, 

 A! sufficiently resembles A (except in the case of metamor- 

 phoses which we have to study) for us to be struck by the 

 resemblances which unite them rather than by the differences 

 which separate them. 



The term heredity in a wide sense is given to the sum total 

 of characters which a body A carries with itself through the 

 changes of its environment. When the animal is adult 

 its heredity as thus denned does not seem to change much ; 

 the modifications which it undergoes, and which it can 

 henceforth carry with it, are light enough to pass unper- 

 ceived and yet they are not, they cannot be null. Each 

 instant the body A subjected to conditions B and executing 

 the function (A x B) becomes ipso facto a new body A l3 

 determined by A and by (A x B). 



We give the name of individual evolution to the series 

 of forms AI, A 2 , A 3 , . . . . A w , taken by the given being 

 A from birth to death through the sums total of circum- 

 stances B l5 B 2 , B 3 , B M . These transformations, as we have 

 seen, are such that the form A 2 is determined by the form 

 A! and by the function (Ai x B t ), which may be expressed 

 by the symbolic formulae 



A! + (A t X Bi) = A 2 



A 2 + (A 2 x B 2 ) = A 3 



A a-1 + (A,.! x E n _ 1 )=A n 



