Uniform Standard for Comparative Animal Psychology. 127 



Ants are articulates, whereas mammals and man 

 belong to the class of vertebrates. Now there is no true 

 anatomical uniformity (homology), but only a greater 

 or a less similarity (analogy) between the sense organs 

 of these two classes. The most perfect sense of the 

 higher vertebrates is undoubtedly that of sight. Yet 

 the eye of vertebrates is totally different in structure 

 from that of the compound (faceted) eye of insects. 

 Whilst it forms only one reverse optic image on the 

 retina of each eye, there is a great divergence of opinion 

 as to the optic effect of the faceted eyes of insects. The 

 older theory of Joh. Mueller, which has been recently 

 supported by such authorities as Exner, Grenadier, etc., 

 holds that the light impressions which are received in 

 the different facets combine behind the point of con- 

 vergence of the crystal-cones, whose number corre- 

 sponds to that of the facets, in the form of a sort of 

 mosaic total perception. This is the so-called theory of 

 mosaic sight. Of late, however, Claparede and Patten 

 maintain that a real image of the object is formed in 

 each of the crystal-cones and that all these images are 

 united to one single sight perception through the com- 

 bination of the different branches of visual nerves. 1 

 The anatomical structure of the compound insect eye, 

 which is so different from ours, easily explains the fact 

 which has been proved by numerous observations, that 

 the sight perfections of insects are far more sensitive 

 of objects in motion than of objects in rest, and more 

 susceptible for differences of color than for differences 

 of shape. An interesting instance hereof is furnished 



l ) See E. Jourdan, "Die Shme und Sinnesorgane der niederea 

 Thiere" (1891), p. 280 ft 



