22, STUDIES IN GENERAL PHYSIOLOGY 
the neighborhood of a box containing the animals, those 
which reacted at all always flew with great violence to the 
side of the vessel which was turned toward the light. In no 
case did they fly in the opposite direction. The experiment 
was unequivocal and could be interpreted in but one way. 
So far as the contact-irritability is concerned, the animals 
collected in the four concave vertical edges when kept in a 
cubical wooden box, which was covered on top with window 
glass. In this position they assumed an indifferent orienta- 
tion toward the source of light. To make perfectly sure of 
this fact, I employed the following method: I placed a 
plate of window glass so close to and parallel with the plane 
of the floor of the vessel containing the animals that they 
could just wedge themselves in between the floor and the 
window glass. The glass plate was entirely exposed to the 
light. Those animals which by chance came to the edge of 
the glass plate crept under it, and remained in this position 
exposed to the light, in contact, however, both above and 
below with solid bodies. On the next day all the animals 
were under the glass plate. The animals are therefore forced 
to bring their bodies in contact with other solid bodies, and 
it is this (and not the light) which causes them to creep 
under solid bodies. I placed a ball of paper in the vessel 
containing the animals; a part of them crept under the paper 
and a part into its folds. In nature these butterflies remain 
in the clefts on the bark of trees or on the ground in mead- 
ows. 
Forficula auricularia are found in great numbers in verti- 
cal crevices (such, e. g., as the spaces between gate and gate- 
post, in the entrance to gardens). I obtained the animals 
for my experiments by hanging a cloth of cotton on the top 
of a small grape vine. The animals collected in the folds of 
the cloth. These animals in reality move away from the 
light ; that is to say, they are negatively heliotropic ; but it 
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