82 University of California Publications in Zoology. [Vol. 4 



react, owing- to a transient physiological state impressed upon it 

 by its recent history. 



A peculiarity of transmission less easy to interpret was shown 

 in the following: observations. A starfish was lying in an ex- 

 tended position, the ai-ms a and e of the bivium projecting in one 

 direction, as in fig. 4. Thus the animal was temporarily bilater- 

 ally symmetrical, with long axis passing through the arm c and 

 between a and €. The right and left sides of this bilateral organ- 

 ism are formed by the outer sides of e-d and a-b. Another star- 

 fish brushed along the outer side of e. At once the rosettes of 



Fig. 4. — Starfish exteixled in sueli a way as to take a bilateral form. See 

 text. 



that region rose to the attack, and also those of the exposed 

 outer sides oi a, b and d — that is, the rosettes of the entire ex- 

 posed outer sides of the rays — while the rosettes of the protected 

 ray c did not respond, nor did those along the protected inner 

 sides of the other four rays. A repetition of the stimulus after 

 subsidence of the rosettes brought about the same peculiar re- 

 sponse. I had no opportunity to study this effect on other speci- 

 mens. 



Influences determining Variation and Modification of Reac- 

 tions in the Pedicellariae. — As we have seen, the behavior of the 

 pedicellariae under given external stimuli is by no means stereo- 

 typed. It depends upon many different conditions, and among 

 these determining conditions are varying internal states of the 

 organism depending largely upon its past history. It will be 

 worth while to summarize here, at the cost of some repetition, the 



