ANTS AND SOME OTHER INSECTS. 15 



of the large worker brain is, moreover, extremely rich in cellular 

 elements. In this connection I would request you to glance at the 

 figures and their explanation. 



Very recently, to be sure, it has come to be the fashion to un- 

 derestimate the importance of brain-morphology in psychology and 

 even in nerve-physiology. But fashions, especially such absurd I 

 ones as this, should have no influence on true investigation. Of 1 

 course, we should not expect anatomy to say what it was never in- 

 tended to say. 



In ants, injury to the cerebrum leads to the same results as in- 

 jury to the brain of the pigeon. 



In this place I would refer you for a fuller account of the de- 

 tails of sensation and the psychic peculiarities of insects to my 

 more extended work above mentioned : Sensations des Insectes. 



It can be demonstrated that insects possess the senses of 

 sight, smell, taste, and touch. The auditory sense is doubtful. 

 Perhaps a sense of touch modified for the perception of delicate 

 vibrations may bear a deceptive resemblance to hearing. A sixth 

 sense has nowhere been shown to occur. A photodermatic sense, 

 modified for light-sensation, must be regarded as a form of the tac- 

 tile sense. It occurs in many insects. This sense is in no respect 

 of an optic nature. In aquatic insects the olfactory and gustatory 

 senses perhaps grade over into each other somewhat (Nagel), since 

 both perceive chemical substances dissolved in the water. 



The visual sense of the facetted eyes is especially adapted for 

 seeing movements, i. e., for perceiving relative changes of position 

 in the retinal image. In flight it is able to localise large spatial 

 areas admirably, but must show less definite contours of the ob- 

 jects than our eyes. The compound eye yields only a single up- 

 right image (Exner), the clearness of which increases with the 

 number of facets and the convexity of the eye. Exner succeeded 

 in photographing this image in the fire-fly (Lampyris). As the 

 eyes are immovable the sight of resting objects soon disappears so 

 far as the resting insect is concerned. For this reason resting in- 

 sects are easily captured when very slowly approached. In flight 

 insects orient themselves in space by means of their compound 



