Physiology of Ventral Nerve Cord of Myriapoda. 283 



equal adaptation in moving either forwards or backwards, just 

 as in the worms. In Scolopendra and Scolopocryptops the legs 

 are the exclusive means of locomotion, whether the progression is 

 hurried or slow. The chitenoid epidermis attains also a greater 

 development in these centipedes. 



Himantarium moves backwards or forwards with equal facility 

 and rapidity. When at rest and touched anteriorly it runs back- 

 wards; on being touched posteriorly it proceeds forwards. Scolo- 

 pendra or Scolopocryptops does not move backwards for any 

 length of time, and nev^er when making haste to escape from dan- 

 ger, as their backward locomotion is much slower than their pro- 

 gression. When Himantarium is beheaded its body keeps run- 

 ning backwards continuously for ten to fifteen min. before it starts 

 to move in either direction, while the decapitated Scolopendra 

 keeps running forwards, no matter what obstacles are placed in 

 its way, and it is very difficult to induce it to walk backwards, 

 even after the excitation from the injury has partly subsided. It 

 is therefore plain that Himantarium and related genera exhibit a 

 less degree of antero-posterior differentiation than do the shorter 

 and stouter centipedes. This is further shown by the fact that 

 when the quiescent Himantarium, which is usually coiled up in a 

 bunch, is gently disturbed by light or by touching it, the two ends 

 of the animal will often be found to crawl or move in opposite 

 directions at the same time, that is, the head end walks forwards, 

 the hind end backwards, till the body is straightened out, when 

 either end may take the lead. This was never observed in Scolo- 

 pendra or Scolopocryptops. 



When Scolopendra or Scolopocryptops are decapitated by re- 

 moving the anterior segment, inflicting as little injury as possible 

 to the body, the body usually continues to move forwards inces- 

 santly and rapidly for five to ten min., lifting the anterior three 

 or four segments next to the wound high up from the ground. 

 After the elapse of a few minutes the body becomes relatively 

 quiescent, usually moving only when stimulated or touched. If 

 placed on its dorsal side, the decapitated animal straightway 

 turns over on its legs. When the posterior part of the body is 

 touched, it either springs forwards or brings the anterior end of 



