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



reaction. If a piece of crab meat is held a little above the dorsal 

 surface of the starfish, so that its juices diffuse against a small 

 spot, the rosettes rise, the pedicellariae open and reach outward, 

 as if to seize the food, and the tube feet appear from below, reach 

 upward and feel about in a searching way. If now the bit of 

 flesh is allowed to drop on the starfish, it is quickly seized, borne 

 to the mouth, and eaten. 



Thus chemical stimuli alone may start the food reaction. 

 Does mechanical stimulation play any part in the matter? When 

 a mechanical stimulus alone, such as a touch with the forceps or 

 a quill, is applied to the dorsal surface of the starfish, usually 

 only the pedicellariae respond, as if in defense, and there is no 

 indication of a food reaction. But this is not always the case. 

 Some individuals send upward their tube feet when thus stimu- 

 lated ; these feel about in the way characteristic of the food re- 

 action. They may even send up the tube feet when pedicellariae 

 are merely nipped off with the scissors. Possibly such individuals 

 are in a state of greater hunger than usual. 



Thus either mechanical or chemical stinnili alone may at times 

 start the food reaction. Chemical stimuli are commonly more 

 effective, and as a rule these must be added to mechanical stimu- 

 lation before the food reaction occurs. 



Of course intense or injurious stimuli of either class do not 

 cause the food reaction. It is as a rule only when there is such 

 a combination of stimuli as might well come from a body fit for 

 food, that the starfish begins the food reaction. Of course, the 

 fact that it may sometimes begin this reaction in response to light 

 mechanical stimuli is quite in harmony with this statement, since 

 such stimuli are commonly the first indications of a body fit for 

 food. 



The main features of the taking of food have now been de-; 

 scribed. There are certain points of interest that did not fall 

 naturally into the general account ; these may be spoken of here. 



As we have seen, the food is often first captured by the pedi- 

 cellariae, and is taken from them by the tube feet and carried to 

 the mouth. Do the pedicellariae release the food, opening of 

 their own motion, when it is taken by the tube feet? Observa- 

 tions directed upon this point seem to show clearly that they do 



