852 STUDIES IN GENERAL PHYSIOLOGY » 
touched a local contraction occurs at the stimulated point, 
but no progressive movements. 
4. If a lateral piece ab is cut from an animal parallel to 
the median plane (Fig. 101), a contraction of the wound results 
which may be so great that the piece rolls up into a spiral. 
(This contraction of the wound-edges 
occurs no matter what the position of 
ya the cut.) The lateral piece ab, which 
contains no brain, executes no pro- 
gressive movements. If, however, a 
contraction of the wound-edge occurs 
in the other piece, so that it is rolled 
into a spiral, the progressive move- 
Qa 
ments no longer occur in a straight 
line but in a circle. I never succeeded 
in bringing about circular movements 
through unilateral destruc- 
3 tion of the brain in Thy- 
FIG. 101 sanozoon. 
II. EXPERIMENTS ON PLANARIA TORVA 
1. The brain and nervous system of the fresh 
water Planarian (Fig. 102, according to Jijima) 
are so analogous to those of the marine Planarian, 
that it is unnecessary for our purposes to give a 
separate description of them. The most important 
difference exists perhaps in the fact that the two 
longitudinal nerves contain certain collections of 
ganglion cells. One might think that the brain FIG. 102 
function of the fresh-water Planarians might also be analogous 
to those of the Polyclads. That is, however, not the case. 
We experience here again what I have pointed out repeatedly 
in my papers on the lower animals: that animals which are 
very closely related morphologically may show the greatest 
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