PART IV 



THE PRIMORDIA 



§42.— THE ADULT STATE IS A STATE OF EQUI- 

 LIBRIUM. — Every living being is at the beginning of its 

 development ^ in a state of unstable equiUbrium. It passes 

 through a series of transformations, brought about by reactions, 

 till there is no longer any force (cause) by which a new reaction 

 might be produced. In this way the individual is brought into 

 a state of stable equilibrium which we call the adult state. 



§ 43.— EACH PRIMORDIUM REPRESENTS A STATE 

 OF EQUILIBRIUM. — As long as we are using the ordinary 

 biological language we may content ourselves with the notion 

 that a given individual is adult. This is, however, a complex 

 notion. When we want to apply the quantitative method we 

 are compelled to decompose the notion adult individual into 

 simple concepts representing measurable things. This is 

 possible by considering each primordium (simple property) 

 separately. 



In the course of the individual development the primordia 

 appear in a certain order. (DARWIN. See § 38, p. 46.) Each 

 primordium is the product of a reaction '^ which begins at a 

 certain moment and continues till there is no longer any force 

 (cause) by which further continuation might be produced. At 

 that moment the material parts which participated in the 

 reaction have reached a state of stable equilibrium : the pri- 

 mordium is adult. 



This brings us to a mechanical definition of the term pri- 

 mordium : a primordium is the expression of a state of equi- 

 librium, or, in short, a primordium is a state of equilibrium. 



The expression adult individual may be used in its ordinary, 

 vague sense. In reality an individual is never adult, because 

 the development of certain of its primordia continues till it has 

 ceased to live. 



§ 44.— INDIVIDUAL ADAPTATION (ACCOMMODA- 

 TION) IS EQUILIBRIUM. (See § 22).— In any reaction (or 



* The beginning of the individual development is very often preceded by a 

 period of rest. 



• Or a series of reactions. 



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