272 



A. J. Carlson. 



When the tension due to the weight of the lever is considerable 

 the segments are kept in constant motion until exhausted. And 

 the same is true if the segmental appendages or legs are able to 

 reach or touch any object. The contact of the legs with any 

 solid object evidently starts reflex movements of locomotion, and 

 for that reason the preparation does not become quiescent until 

 nearly exhausted when fixed to the platform ventral side down 

 so that the ambulatory appendages are in contact with the board. 

 When the anterior end of the centipede serves as the reacting 

 portion the reflex restlessness is much greater than when the pos- 

 terior segments are employed. This is true whether the head seg- 

 ment is removed or not. The measurements of the rapidity of 

 conduction of the postero-anterior impulses in the cord by the pres- 

 ent method is therefore attended with greater diflliculties than the 



Fig. 3. — Scolopaidra. 



Tracings of the contraction of the posterior segments on distal and proxi- 

 mal stimulation of the cord. Length of cord, 6 cm. Transmission time of the 

 impulse, 0.022 sec. Rate, 2.70 m. per sec. Time, 100 d. v. per sec. 



measurement of the antero-posterior rate. In the millipede the 

 union of the segments admits of only slight elongation and con- 

 traction of the body, but the body may be coiled by contraction 

 of the ventral muscles in the segments. The amplitude of this 

 contraction is much greater in the posterior than in the anterior 



