230 Animal coloration. 



If, in pursuing a straight course, the creature haps on a- 

 gap between the obstacles, it naturally takes advantage of 

 this, as indeed a beetle would do ; but if across its road there- 

 intervene an upright obstacle, the Hymenopteron continues to- 

 direct itself towards it, evidently without perceiving it, or at 

 any rate without perceiving it distinctly, until the insect's 

 body, or a portion of its body, has penetrated into the shadow. 

 Instantly the insect receives a general ximpressio7i (impression, 

 that may be either dermatoptic or visual, possibly both) ; it 

 then hesitates for a very brief instant, then alters its course to 

 a right angle, makes literally a half-turn to the right or to the 

 left, proceeds parallel to the outline of the shadow, then again 

 resumes its course towards the source of light, making again 

 a similar change of direction when it again passes into the 

 shadow of a fresh obstacle." 



It should be explained that the " maze " referred to in his 

 description consists of a number of pieces of wood arranged in 

 a series of concentric circles, something after the fashion of 

 restorations of Stonehenge. In the circles, the pieces are in- 

 terrupted by intervals, and each interval is covered or nearly 

 covered by a piece belonging to the next circle ; there is thus 

 no possibility of an insect, placed in the centre of the maze, 

 seeing its way out 'at once. 



The vertebrates experimented with found their way out by 

 the shortest route, making their way directly from one interval 

 to another, and avoiding the obstacles ; the way in which the 

 Hymenopteron proceeds indicates that it is largely guided by 

 the sensations from the distinctions between light and shade. 

 This does not look as if a clear appreciation of form re- 

 semblances were possible. Dr. Sharp, at the conclusion of his 

 review, remarks that " there is at present no evidence at all 

 that the light perceptions of insects are sufficiently complex to- 



