TRANSFORMISM 219 



active. In general, the continued use of an organ 

 leads to its increase in size and efficiency, and con- 

 versely disuse leads to a decrease of size and even 

 to atrophy. 



The essence of an adaptation is that it is an active, 

 purposeful change of behaviour, or functioning, or 

 morphology, by which the organism responds to some 

 change in its physical environment, or to some other 

 change in its own behaviour, or functioning, or mor- 

 phology. It is also a change which remains as a 

 permanent character in the organisation of the animal 

 exhibiting it. It does not matter even if the change 

 of behaviour is one which is willed in response to 

 some change of environment actually experienced, or 

 whether it anticipates some change that is foreseen. 

 A changed mode of behaviour adapted intelligently 

 leaves, at the least, a memory which becomes a per- 

 manent part of the consciousness of the animal, and 

 may influence its future actions ; or if it is evoked by 

 a process of education it must involve the establish- 

 ment of a " motor habit." The education of a singer 

 sets up, in the cortex and lower centres of the brain, 

 a nervous mechanism which controls and co-ordinates 

 the muscles of the chest and larynx, and which did not 

 exist prior to the process of education. Adaptations 

 are therefore acquired changes of some kind or other 

 by means of which the organism is able to exert a 

 greater degree of mastery over its environment, in- 

 cluding in the latter both the inert matter of inorganic 

 nature and the other organisms with which the animal 

 competes. 



They are acquirements because of which the organ- 

 ism deviates from the morphological structure char- 

 acteristic of the species to which it belongs. Do they 

 affect the entire organisation of the animal exhibiting 



