286 A.J. Carlson. 



tact with the centipedes, the body jerks back, and both modes of 

 locomotion are usually employed in getting away. That the re- 

 action is more pronounced when the posterior end of the body 

 makes the contact is probably due to reduced excitability of the 

 anterior segments next to the wound. The decapitated animal 

 continues to react in this manner for several days. 



The decapitated Himantarium retreats from water just as the 

 intact individual, but on coming in contact with other objects in 

 its path it simply walks over or around them. When, however, 

 a solid object, like a pencil or a pair of forceps, is moved towards 

 the crawling centipede and the contact thus made, the decapitated 

 animal usually retreats. When the body comes in contact with 

 an object which is moving towards it, the impact is necessarily 

 stronger than when the object is stationary and the centipede alone 

 moving, hence the difference in the motor reaction is probably 

 due to the quantitative difference in the sensory impulses. But 

 the decapitated Himantarium jerks back and retreats from Scolo- 

 pendra and Scolopocryptops even when these latter lie perfectly 

 dormant, so that the reaction cannot be explained on that ground. 

 One further possibility must be investigated before this reaction 

 can be ascribed to a qualitative discrimination in the motor reac- 

 tions to touch impressions on the part of the decapitated centi- 

 pede. The touch impressions may namely be supplemented by 

 those of temperature. I have made no measurements of the body 

 temperature of these animals, and until such determinations are 

 made this interesting point must be left undecided. 



Cross-section of the ventral nerve-cord in any part of the body 

 destroys the coordination between the two ends of the body on 

 either side of the lesion just as effectively as when the whole body 

 is cut transversely and the two parts rejoined by a thread or a wire. 

 The lesion does not destroy the coordinated locomotion of either 

 half, but the direction of the locomotion of the anterior half may 

 or may not be the same as that of the posterior half. When the 

 direction is not the same, a "tug of war" ensues, in which the 

 portion having the greatest number of segments or having the 

 most favorable ground for contact for Its legs comes out victo- 

 rious. Scolopendra usually turns about and bites its refractory 

 hind body repeatedly. 



