636 T^AYMOND TEARL. 



After the worm Ims been feeding for n, certnin leno-tli of 

 time it will detach the phaiynx and spontaneously move off 

 from the food, the pharynx: being withdrawn again into its 

 sac. The length of time after the beginning of the feeding 

 at which this takes place varies very greatly in different 

 cases. I have observed a specimen which fed on a piece of 

 mollusc for as long as an hour and thirty minutes, while in 

 other cases the worm may stay on the food only ten minutes, 

 or even less. Judging from the rate at which food is taken 

 np while the animal is feeding during the day, and from the 

 fact that pieces of meat left in the dish overnight are almost 

 entirely consumed by morning, it would appear that much of 

 the time during the night is spent in feeding when any 

 material available for the purpose is at hand. While the 

 anterior end of the feeding worm retains its normal sensi- 

 tiveness to stimuli, it nevertheless requires considerable 

 stimulation to induce a feeding worm to leave the food. 

 Shaking of the dish, which would ordinarily set all resting 

 specimens into rapid movement, has little or no effect on 

 feeding specimens. If a worm is suddenly pulled off a piece 

 of meat on which it is feeding a very good view of the 

 extruded pharynx may usually be had, as this organ is 

 retracted somewhat slowly when torn from food in this way. 



So far as I have been able to discover, the presence of 

 food in the immediate neighbourhood of a resting planarian 

 has no effect upon it. Apparently the stimulus afforded by 

 crushed meat is not sufficiently strong to produce a response 

 from such an individual. The following experiment copied 

 from my notes will show this. 



May 14th, 1901, 3.10 p.m. — A piece of freshly crushed 

 snail was placed 1 mm. distant from the anterior end of a 

 resting specimen. No reaction or other effect produced. 



3.30 p.m. — Worm in same position as before. 



4.5 p.m. — No change. (At this time the worm was acci- 

 dentally started into movement and the experiment conse- 

 quently ended.) 



This lack of effect of food on resting specimens may be 



