MUTABILITY. 1 73 



more detail, processes are frequently abridged or totally 

 omitted which once, while they were being acquired 

 and after they had been established, occupied a longer 

 period, but in the course of selection either became of 

 less importance to the individual, or preserved a physio- 

 logical value only as phases of transition. 



The second great class of characters, namely, those 

 which have been newly acquired and depend on adap- 

 tation, 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 emit- 

 ting, and its stability is therefore constantly dependent 

 on the supply of material for its functions. For nutri- 

 tion, which generally and wholly determines the external 

 appearance and the nature of the individual, is accom- 

 plished by the innumerable cells and their derivatives. 

 Every fluctuation 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 structure 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 

 elementary 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 



