MOVEMENTS, KTf'., OE FIJESTT-WATER PLANA IITANS. 039 



it contracts I'lijtliinically in a longitndinnl direction for n 

 time, and then comes to rest at about its normal Icuotli wlien 

 in the body. Mechanical stimnlation causes merely lono'i- 

 tudinal contraction, Avhile the presence of food near it has no 

 effect whatever. Freslily crushed snail meat placed Avithin a 

 millimetre of such an isolated pharynx had no effect upon it 

 in the course of an honr. 1 have tried layino- the isolated 

 pharynx directly on pieces of meat to see if there would be 

 any tendency for the end of the orc^an to attach itself as it 

 normally does. This was not done, nor was any other 

 definite reaction produced. 



These operation experiments show, so far as they pfo, that — 



(1) The presence of the pharynx in the body (i.e., the 

 functional ability to take food) has nothing to do with deter- 

 mining- the reaction of the anterior end of the bod}^ to food 

 stimuli. The anterior part of the body gives the same re- 

 action to food in every case, without regard to whether so 

 doing actually puts the animal in a position to get food oi' 

 not. The i*eaction is only purposive under certain circum- 

 stances; when changed conditions make it no longer purpo- 

 sive, no adaptive change in the behaviour of the anterior end 

 occurs. This shows clearly how little basis there is for con- 

 sidering the behaviour towards food as anything of the 

 nature of intelligent behaviour. 



(2) The stopping of the worm on the food under normal 

 circumstances is due to the posterior half of the body, not the 

 anterior. The behaviour of the anterior cut piece in gliding 

 directly over the food is what one might be led to expect from 

 the behaviour of the same part of the body under normal 

 circumstances. As described above^ it was seen that the 

 anterior end of the normal individual gives every appearance 

 of attempting to continue moving forward while the posterior 

 part is feeding, and is only prevented from doing this by the 

 mechanical hindrance of the attached pharynx. In a sense, 

 we may consider that in a large degree the work of tlie 

 anterior end of the body with reference to feeding is over 

 when it gets the animal up on to the food. 



