240 BEHAVIOR OF THE LOWER ORGANISMS 



face of attachment always occurs, and according as this is convex, con- 

 cave, smooth, rough, or inclined, is the turning process made easier or 

 more difficult, and brought about in this manner or that" (1886, pp. 107- 

 108). Sometimes the animal turns a somersault; sometimes it extends 

 all its arms upward, taking the "tulip" form and toppling over on one 

 side — and so on through many variations. 



Even the main features of the typical reaction may be omitted or 

 changed, the turning taking place by means quite different from the 

 usual ones. Thus, Astro pecten aiirantiacus usually rights itself by 

 means of its tube feet, but sometimes turns without using the tube feet 

 at all. Lying on its back, it lifts the central disk high, resting on the 

 tips of three or four of the arms. Then it turns two of the arms under, 

 while lifting the others upward, so that it now falls with ventral side 

 down. During this action the tube feet are moved about in a lively 

 way, and when the turning is nearly completed the tube feet of the 

 upper radii which are approaching the substratum are pushed far out, 

 as if preparatory to meeting the bottom. 



When a portion of the feet were prevented from acting, by subjecting 

 them to alcohol or other drugs, Preyer found that the starfish righted 

 itself by means of the remaining ones, and by bending and twisting its 

 arms. Pieces of the arms may right themselves, and this again occurs 

 in many different ways. 



The thorough study of the movements and reactions of the starfish 

 made by Preyer (1886) shows that the righting reaction is typical of the 

 entire behavior. If the starfish is suspended just below the surface of 

 the water with ventral side up, by threads attached to the tips of its 

 arms, it performs varied movements, until in the course of time it turns 

 over, just as in the usual righting reaction. If a short rubber tube was 

 slipped over one of the arms of a brittle star, to its base, Preyer found 

 that this caused the animal to perform many varied movements, till by 

 one of them the tube was removed. Sometimes the animal merely 

 moved rapidly forward, dragging the arm bearing the tube behind it 

 till the tube was scraped off. Sometimes the animal placed one or two 

 of the other arms against the tube and forced it off. In other cases the 

 covered arm was dropped from the body (as often happens in brittle 

 stars). Again, sometimes the arm bearing the tube was lifted and 

 waved back and forth, till the tube was in this way displaced. Thus 

 Preyer observed five different ways in which the tube was finally re- 

 moved; as he remarks, "If one method does not help, another is used." 

 It may, of course, be maintained that in all these cases the removal of 

 the tube was in a sense accidental. But this is precisely the essential 

 point in much of the behavior of lower organisms. When stimulated 



