ANIMAL BEHAVIOUR 189 



or Aiptasia will refuse to take bits of filter paper, though 

 it will still take meat. " After it has thus refused paper, 

 two or three pieces of meat are given in succession, and 

 taken readily. Now the bit of paper is placed again on the 

 disc, and it too is swallowed. Clearly, the uninterrupted 

 taking of a number of pieces of meat changes the physiologi- 

 cal condition in some way, preparing the animal for the 

 taking of any object with which it comes in contact. One 

 cannot fail to note the parallelism with what occurs in higher 

 animals under similar conditions " (Jennings, 1906, p. 226). 

 We see, then, that in relatively simple creatures, such as 

 sea-anemones and starfishes, which have no nerve-ganglia, 

 past stimuli and past reactions are important factors in 

 determining present behaviour. Thus an elongated sea- 

 anemone, Aiptasia annulata, which lives in crevices beneath 

 and between stones, will bend into a new position if it 

 is touched too often, and if it be molested still further 

 will release its foothold and move to a new region (p. 206). 

 In its natural surroundings it often has to cramp its 

 body into quaint zigzag shapes, and a point of some 

 interest is that this may become habitual and may per- 

 sist for some time after the creature is removed to an 

 unimpeded habitat. This illustrates what is meant by 

 registration. 



In his valuable study of the behaviour of the earthworm, 

 Prof. H. S. Jennings shows that the response to a stimulus 

 depends on external factors (such as the intensity and locali- 

 sation of the stimulus), and on internal factors (such as 

 the state of the animal at the time, its tendency to move 

 in a certain way, e.g., head foremost, and the direction in 

 whicli it was crawling at the time). But what is particu- 

 larly interesting is the definite evidence that the behaviour 



