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 Coccinellid<, 

 to which I have already referred in my former paper on the 

 "Orientation of Animals toward the Center of Gravity of the 

 Earth." l 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 CocciiiellidaB. 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 Coccinellidse, 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) trliirh /iitf t/tc median plane of their bodies in 



iSitzunysberichte der Wiirzburyer physikalisch-medicinischen Gesellschaft, 1888. 



