190 ANIMAL BEHAVIOUR 



at a given time depends on past experiences on former ex- 

 ternal conditions and on former actions. 



Succession of Tentative Reflexes. Because of the abun- 

 dance of reflexes in the simpler animals the impression has 

 gained ground that behaviour in these lower reaches of life 

 is very stereotyped. But this impression requires critical 

 consideration. When a particular reflex action solves a par- 

 ticular problem at a stroke, there is no more to be done. 

 But the problem is often more difficult, and what the creature 

 does is to exhibit varied movements and to select certain 

 resulting conditions. Even in such predominantly reflex 

 creatures as sea-urchins, the tube-feet, spines, and pedicel- 

 lariae may in difficult situations continue in varied tentative 

 movements, as if trying all expedients, and long after the 

 original stimulation has ceased. The ' righting ' reaction 

 of an ' inverted ' starfish is singularly varied and flexible. 

 Professor Preyer repeatedly slipped a short india-rubber tube 

 over one of the arms of a brittle star, and observed five 

 different ways in which it was removed, including, it must 

 be confessed, as one desperate method, the surrender of the 

 arm itself. As the observer remarked, " If one method does 

 not help, another is used." 



Professor Preyer's experiments on pegging down starfishes 

 (of course without injuring them) revealed extraordinary flex- 

 ibility of behaviour and also a shortening of the time required 

 for escape. The number of useless movements, " superfluous 

 twistings, feelings about, and forward and backward mo- 

 tions ", becomes less the oftener the individual has been 

 placed in such a situation. If this is true (Prof. Jennings 

 notes), we have in so low an animal as the starfish regulation 

 through the selection of conditions produced by varied move- 

 ments passing into a more directly regulatory action; in other 



