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... 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. 
Vv. 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 
1Grundlinien zur Erforschung des Helligkeits- und Farbensinnes der Thiere, 
Prague (1884), p. 290. 
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