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 

 emitting, and its stability is therefore constantly depen- 

 dent 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 deriva- 

 tives. Every fluctuation of supply in any part of the 

 organism, nay, in any point in the surface of a microsco- 

 pic reef-builder, must necessarily involve a modification of 

 textural parts, or of integrated textural groups or organs. 

 Mutability is thus a character resulting from the 

 intrinsic 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 



