86 STUDIES IN GENERAL PHYSIOLOGY 
beetles) is somewhat remarkable, as many other animals, such 
as caterpillars, plant lice, etc., do not react geotropically 
after they have been kept in the dark for some time. 
3. Another phenomenon can be observed in Coccinellide, 
to which I have already referred in my former paper on the 
“Orientation of Animals toward the Center of Gravity of the 
Earth.’’! Cockroaches, for example, usually assume a position 
on the vertical walls of boxes ; they never remain for any length 
of time on the horizontal bottom, where their ventral surfaces 
are turned toward the center of gravity. If, for example, 
the roaches are scattered about on the four vertical walls of 
a box, and the box is carefully and slowly turned through an 
angle of 90° on a horizontal axis, only those animals whose 
ventral surfaces are turned toward the center of gravity in 
the new position begin to move. They leave the plane on 
which they were up to the time the box was turned and again 
seek a vertical plane from which to suspend themselves. Yet 
the animals on the other three vertical walls remain at rest 
while the box is turned. This seems to indicate that the 
animals cannot turn their ventral surfaces toward the center 
of gravity for a long time. Whether this means that the 
animals’ extremities can bear the pull of the load of the body 
better than its pressure, I cannot say. The same phenome- 
non is also observed in Coccinellide. If the box is placed 
obliquely, the two oblique planes on which the animals turn 
their ventral surfaces toward the center of gravity are first 
abandoned. 
4. Aside from the peculiarity which has been mentioned, 
the Coccinellide, like roaches, are found hanging on walls 
in all possible orientations toward the center of gravity of 
the earth. Great differences are therefore found in this 
regard also, for there are animals (such as the newly hatched 
Lepidoptera) which put the median plane of their bodies in 
1Sitzungsberichte der Wtrzburger physikalisch-medicinischen Gesellschaft, 1888. 
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