48 DEVELOPMENT AND PURPOSE CHAP. 



animals, and it is possible for a good observer to give a 

 fairly complete inventory of the ' action system ' of a 

 Rhizopod or an Infusorian. The animal is in constant 

 movement of the parts or the whole. The movements are 

 not dependent on any special stimuli. They go on c of 

 themselves 5 under normal conditions, though they are 

 affected in detail by the temporary state of the animal, e.g. 

 by emptiness or satiety. Finally, they serve the simple 

 life-needs, absorbing food, sometimes (not always) reject- 

 ing unsuitable matter, avoiding harmful objects, and 

 (principally by the indirect method of avoiding other 

 regions) guiding the animal to a suitable environment. In 

 the successful maintenance of this behaviour there is often 

 need for a special combination of particular actions, and 

 here there is room for a certain variation from case to case. 

 But the elements of the combination are always easily 

 recognisable type reactions, the beat of cilia, movements 

 of the body on its axis, contractions to this side or that, or 

 whatever it be. There is always a need for definite 

 responses to certain stimuli if these occur, but the evidence 

 is clear that the normal activity is not merely a series of 

 responses to special stimuli, but the outcome of the internal 

 forces of the organism, that is to say, of the congenital 

 structure. 1 As such we may speak of it as inherent struc- 

 tural activity, 2 and we may lay it down that the simplest 

 and most general form of correlation in behaviour is the 

 broad adaptation of the lines of action to the general needs 

 of life effected by the congenital structure in accordance 

 with its internal forces. The cause of this correlation 

 according to ordinary biological theory is inheritance from 

 generations whose individuals survived or perished in 

 proportion as their structure was well or ill adapted to life 

 conditions. The degree of correlation thus determined 



1 The remarks of Loeb and others (Sixth International Congress of 

 Psychology, 1910) do not so much as touch the facts reported by 

 Jennings in his masterly Behaviour of the Lower Organisms (1906). 



2 The term * structural activity ' would, as will be seen immediately, 

 include the reflex. The qualification 'inherent' distinguishes actions 

 or those elements in action which depend on internal forces from those 

 requiring a special stimulus to set them going. 



