FEEDING REACTIONS OF PLANARIA MACULATA. 69 



are extracted. But given a sensitive preparation of which any 

 number can be obtained the reaction is as follows : When placed 

 in a dish of water close to a piece of liver, the pharynx elongates 

 actively, its delicate lip is extended into a broad funnel, the 

 walls of which undulate constantly, receiving and being directed 

 by the stimulating substances of the meat-juice. The result is 

 that the funnel is pointed toward the meat, and not only so 

 but the whole pharynx moves forward sometimes several milli- 

 meters by a very wormlike series of extensions, contractions and 

 wrigglings until the mouth comes into direct contact with the 

 meat. There is no doubt of the power of the pharynx to orient 

 itself toward the source of diffusing juice and its ability to move 

 toward that source. 



The feeding reaction of the pharynx upon reaching the meat is 

 of enough interest to deserve description. Contact of the mouth 

 with the meat causes a wave of peristalsis to pass almost instantly 

 through the pharynx and as a result a mass of food is discharged 

 from the end of the pharynx to which the intestine would 

 normally be attached. Other waves follow in quick succession 

 and the consumed food is discharged at each wave with con- 

 siderable force. This activity continues for many minutes and 

 results in the accumulation of a surprisingly large heap of food. 

 The shape of the passage through the pharynx is more or less 

 maintained by the masses of food and the little strings of food 

 particles show a tenacity which indicates that the pharynx has 

 added a secretion probably of a mucous nature to the substance 

 passing through it. The experiment can be duplicated with 

 liver extract or yolk of egg dropped carefully on to the bottom of 

 a dish containing water. The pharynx will work its way into 

 the substance and move sometimes a considerable distance in 

 irregular course through it. During the movement it is con- 

 stantly eating and leaving behind a trail of consumed food. 

 While this reaction is in progress the pharynx bears a remarkable 

 resemblance to a whole organism. The casual observer would 

 immediately call it a living worm. Such entire maintenance of 

 function by an isolated organ is certainly unusual. 



