356 STUDIES IN GENERAL PHYSIOLOGY 
in plants also, but in the latter case through different 
mechanisms. These facts which I considered as self-evident 
have been misunderstood by one author and have been falsely 
represented, as though I had asserted that brain and eyes 
are superfluous. 
From what I said it also followed that in animals which 
possess eyes the sensitiveness to light need not by any means 
be limited to the eyes. Photosensitive elements may be 
found also in other portions of the surface of the body. 
Graber has in fact already reported experiments on Tritons 
and angleworms which he claims point in the same direction. 
It could, moreover, be foreseen that an effect of light might 
perhaps be possible in many animals without the existence 
of a true reflex arc, for I found in Ciona intestinalis that a 
typical reflex phenomenon continues to exist in this animal 
after destruction of the central nervous system. There was 
finally the possibility also that both conditions might be 
found together in the same animal. The latter is the case 
in Planaria torva, determined to be such by Dr. Wheeler. 
4. After what has been said it is scarcely necessary to 
emphasize the fact that brainless pieces of Planaria torva will 
not assume the dorsal position any more than will uninjured 
animals. All my experiments to bring about forced move- 
ments in these animals through unilateral destruction of the 
brain remain as fruitless as in Thysanozoon. 
III. EXPERIMENTS IN CEREBRATULUS MARGINATUS 
The Nemertines possess a more highly developed brain 
than do the Planarians. The brain is larger and shows alsoa 
greater subdivision into smaller parts. It also is continued 
into two lateral nervous cords. The latter contain ‘‘a super- 
ficial covering of ganglion cells which may give rise to 
ganglion-like swellings at the points where the nerves 
branch.”” 
1CxLaus, Lehrbuch der Zoologie, 4. Aufl., p. 336. 
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