572 RAYMOND PEAEL. 



slowly, and come to rest sooner. At the same time the 

 anterior pieces will appear more and more like the normal. 

 In both sets of pieces the crawling movement may be in- 

 duced by proper stimulation of the posterior ends. 



01)lique transverse cuts produce the same results as do 



A 



B 



Fig. 11.— Operation diagram. Heavy lines indicate the cuts made. 

 For results see text. 



direct ones. The same laws hold as to the movements of the 

 pieces. In case a strip is cut from the side of the body, as 

 shown in Fig. 11, the smaller piece A curls np, and does not 

 make any further progressive movements, although it 

 remains alive, and will eventually regenerate in most cases. 

 The main part B contracts on the cut side, and hence becomes 

 curved in that direction after the operation. It is able to 

 move about, but at a somewhat slower gliding rate than 

 normal, and in a path curved towards the cut side. In case 

 a worm is slit down the middle line at the anterior end, as in 

 Fig. 12, it is able to glide, but at a slower rate than 

 normal. It performs the crawling movement in response 

 to stimulation at the posterior end, and each half of the head 

 performs feeling movements independently of the other half. 



Fig. 12.— Operation diagram. The heavy line indicates the cut 

 made. For results see text. 



An individual slit up in the middle line from the posterior 

 end, as in Fig. 13, glides at approximately the normal rate, 

 provided the cut is not carried too far forward. If the cut 

 extends into the head region the gliding becomes im- 

 mediately slow^er. Such a specimen performs the crawling 



