JenninGvS, UcxkilU on Physiology of Behavior. 319 



They carry it about, toward food and away from danger, keep the 

 sea iirehin clean, capture prey, combat against enemies, and all 

 together do the work of life in a competent way. This is brought 

 about without any regulation by a "higher center," merely through 

 the essentially in(lc])ciident activities of the various ])arts. Therefore 

 the sea urchin is characterized as a '"republic of reflexes." The 

 ap]>arent unity of action is due merely to the way the different 

 actions of the different parts fit into one another, by a sort of preestab- 

 lished harmony. "It is not that the action is unified, but that the 

 movements are ordered ; that is, the setting off of the different reflexes 

 is not the result of a common central impulse, but the separate reflex 

 arcs are so constructed and so fitted together that the synchronous 

 but independent setting off of the reflexes, as a result of an external 

 stimulus, produces a definite general action of the animal, just as 

 happens in animals in which a common center })roduces the actions" 

 (16, p. 390). "When a dog runs, the animal moves its feet. When 

 the sea urchin runs, the feet move the animal" (11), p. 7-3). 



But the author finds that the separate reflex-])ersons are not abso- 

 lutely independent ; impulses may pass from one to the other, in 

 such a way as to produce a unified action of all. But this is due 

 merely to a set of nerve nets having a special arrangement; it is 

 a matter of interconnections, not of regulation from a ^'higher 

 center." The question may be raised whether this distinction docs 

 not depend on an undefined and mystical use of the term higher 

 center. If the higher center, in accordance with the illuminating 

 ideas of Loeb, is after all essentially a place for complex inter- 

 connections, then the difference between the sea ui'cdiin and higher 

 animals is only one of degree. 



Von Uexkiill finds that the separate reflexes of the various organs 

 arc not absolutely stereotyped, but the action of each part is 

 changed at times in certain ways, often depending <>\\ the action of 

 neighboring parts. We have then in the sea urchin an opportunity 

 of studying coordination in its most elementary condition, and thus 

 perhaps of determining the fundamental nature of the phenomena 

 involved. This aninnd is a sort of model, which can be taken to 

 pieces Avitliont serious ultci'ation of the action ni the [)arts; yet in 



