MUTABILITY. 



173 



after they had been established, occupied a longer period^ 

 but in the course of selection either became of less im- 

 portance to the individual, or preserved a physiological 

 value only as phases of transition. 



The second great class of characters, namely, those 

 which have been newly acquired and depend on adapta- 

 tion, pre- suppose the mutability of the organism. This 

 is a fundamental phenomenon of organic bodies. It is 

 inherent in the minutest morphological constituents, in 

 protoplasm, and in cells, and in the morphological ele- 

 ments evolved from them, the pervading and determining 

 individual life of which results in the collective life of the 

 creature. The organic morphological element is in a state 

 of saturation; it is continually imbibing and emitting, 

 and its stability is therefore constantly dependent on the 

 supply of material for its functions. For nutrition, which 

 generally and wholly determines the external appearance 

 and the nature of the individual, is accomplished by the 

 innumerable cells and their derivatives. Every fluctua- 

 tion of supply to any part of the organism, nay, to a 

 single point of the surface of a microscopic atom, must 

 involve a modification of textural parts, or in the struc- 

 ture of integrated textural groups or organs. 



Mutability is thus a character resulting from the in- 

 trinsic nature of organism, and dependent on external 

 conditions, which determine quantity and form, as well 

 as the development and transformation of the ele- 

 mentary constituents, or their abortion and retro- 

 gression. These effects may be exhibited in a polype- 

 stem, which as a whole represents the individual, in its 

 single polypes, the cells and morphological elements. 

 The single individuals are alike in their constitution, but 



