STEREOTROPISM 135 



still lacking and we must be satisfied with a few descriptive 

 remarks. 



Certain animals show a tendency to bring their body 

 completely into contact with solid bodies, e.g., by creeping 

 into crevices. Without further experimental test this 

 might appear as an expression of negative heliotropism, 

 but it can be shown that this assumption would be wrong. 

 Amphipyra is a positively heliotropic butterfly which, in 

 spite of its positive heliotropism, shows the peculiarity 

 that it creeps into crevices when given an opportunity. 

 Such animals were kept in a box at the bottom of which 

 was a square glass plate resting with its four corners 

 on supports just high enough to allow the animals to creep 

 under the glass plate. After some time every Amphipyra 

 was found under the glass plate. This happened also 

 when the glass plate was exposed to full sunshine, while 

 the rest of the box was in the shade. 287 



The same stereotropism is found in female ants at 

 the time of sexual maturity. When such animals are put 

 into a box containing folded pieces of paper or of cloth, 

 after some time every individual is found inside the folds. 

 This happens also when the boxes are kept in the dark. 287 



The same form of stereotropism is found in many 

 species of worms. When earthworms are kept in jars with 

 vertical walls they are found creeping in the corners 

 where their body is as much as possible in contact with 

 solid bodies. It is this tropism which compels the animals 

 to burrow into the ground. 



Maxwell 349 kept Nereis, a form of marine worms, 

 which burrows in sand, in a porcelain dish free from sand. 

 Into the dish glass tubes were put, whose diameter was 

 of the order of that of the worms. After 24 hours every 

 tube was inhabited by a worm who made it its permanent 



