408 Experiments on the vision of Arthropods. 



2. That there is at present no evidence at all that the 

 light-perceptions are sufficiently complex to be entitled 

 to be called seeing ; but that, as the large development 

 of the compound eye permits the simultaneous perception 

 of movement, its direction, and of lights and shades 

 over a certain area, a dragon-fly may pursue and capture 

 another insect without seeing it in our sense of the 

 word seeing. 



Explanation of Plate XIII. 



Fig. 1. Plan of the maze used by Plateau, a, a, a, the undu 

 latory track of an animal with good sight (vertebrate) when 

 escaping ; b, h, b, zigzag track of an insect that detects the presence 

 of the pieces by means of their shadows (Hymenoptera) ; c, c, c, 

 track of an insect that runs against the objects (Coleoptera, e.g.). 



Fig. 2. Some of the pieces of the maze, with the shadows and 

 penumbrae cast by them, o, o, o, track of a hymeuopteron turning 

 aside only when it enters the deep shadow; l^V^P^ track of a 

 hymenopteron sensitive enough to perceive the penumbra. 



Fig. 3. General view of the maze as used by Plateau. 



Copied by permission from Professor Plateau's memoirs. 



