MOVEMENTS, ETC., OE ERERII-WATER ET.ANAI-'TANS. 689 



it contrncts I'liytlimically in a longitiuliiial diroction for a 

 tim'e, and tlien conies to rest at al)ont its normal length when 

 in the body. Mechanical stimnlation canses merely long'i- 

 tndinal contraction, while the presence of food near it has no 

 effect whatever. Freshly crashed snail meat placed within a 

 millimetre of such an isolated pharynx had no effect upon it 

 in the course of an hour. I have tried laying- the isolated 

 phai"ynx directly on pieces of meat to see if there would be 

 any tendenc}'^ for the end of the organ to nttncli itself as it 

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

 definite reaction produced. 



These operation experiments show, so far as the_v go, that — 



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

 functional abilit}' to take food) has nothing- to do with deter- 

 mining the reaction of the anterior end of the body 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 or 

 not. The reaction 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 behavionr 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 wdiile the posterior 

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

 mechanical hindrance of the attached pharynx. In a sense, 

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

 anterior end of the body with reference to feeding- is over 

 when it gets the animal up on to the food. 



