358 STUDIES IN GENERAL PHYSIOLOGY 



locomotion as two Individuals, or perhaps that the posterior portion 

 would simply be dragged along passively. Neither, however, occurs. 

 The animals which lack entirely a portion of the central nervous 

 system creep about as normal animals, except for a slight variation 

 which will be described later. A contraction of the longitudinal 

 muscles begins in the anterior segments which passes posteriorly, 

 reaches the operated point, jumps over it, and continues behind it, 

 so that the movements of both parts are co-ordinated in exactly the 

 same way as in the normal animal. 



To explain this remarkable phenomenon Friedlander 

 assumes that a ''longitudinal pull" is exerted upon the poste- 

 rior segments through the contraction of the anterior seg- 

 ments. "This acts as a stimulus to the stretched portions of 

 the abdominal nerve cord, and the reflex brought about thereby 

 consists of a contraction of the longitudinal muscles of the 

 stretched segments." The longitudinal stretching of the 

 skin (not of the abdominal nerve cord) would therefore lib- 

 erate reflexly a longitudinal contraction. The correctness of 

 this idea was proved by the following experiment. An angle- 

 worm is cut in two in the middle and both pieces are sewed 

 together in such a way that they are connected by a thread 

 about 1 cm. long. The pieces when connected in this way 

 by means of a thread execute co-ordinated movements. 



Graber tested the statement of Hofmeister and Darwin 

 that the anterior end of the body of the angleworm is sensi- 

 tive to light. 1 He amputated the anterior segments of angle- 

 worms, and found that the brainless pieces were still sensi- 

 tive to light. The reaction of the angleworm to light is 

 therefore no function of the brain alone. My own experi- 

 ments consisted in amplifying these facts in some directions. 



V. EXPERIMENTS ON NEREIS 



If a Nereis is cut into several pieces, only the oral piece 

 retains the power of burying itself in the sand. Earlier 



1 Grundlinien zur Erforschung des Helligkeits- und Farbensinn.es der Thiere, 

 Prague (.1884,1, p. -90. 



