66 University of California Puhlications in Zoology. [Vol. 4 



more. They are likely to be found chiefly in the region of the 

 junction of the rays with the disk, though they may occur else- 

 where. After the eye has become accustomed to studying with 

 the lens the numerous minute pedicellariae surrounding the 

 spines, it is almost startling to come suddenly upon one of these 

 monsters, often gaping widely so as to remind one of the hippo- 

 potamus in the circus posters, and showing even to the naked 

 eye a formidable set of teeth. Their behavior is different in 

 many ways from that of the other pedicellariae, so that we shall 

 take it up separately. 



Fig. 3.^ — Pedieellaria. showing the three pieces of which it is composed, 

 and the muscles by which it is opened and closed. After von Uexkiill. 



In addition to these two kinds, there are in some individuals 

 a few examples of a third sort of pedicellariae. These are little 

 larger than the ordinary type, but have the same structure as 

 the large pedicellariae just described. They are usually found 

 scattered near the madreporic plate and in the region of the 

 angle between the rays. We shall not deal separately with their 

 behavior. 



Action System. — The main actions of the pedicellariae are 

 their movements of attack, and of withdrawal. In the former 

 they rise to the top of the spines, open, seize an object with which 

 they may come in contact, and hold to it. Under certain other 

 conditions they withdraw and close. We wish to determine just 



