496 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



The indistinctness produced by distance has the effect of reducing 

 the image of (e. g.) an Ailanihus leaf to an outline in which the 

 different lobes are almost entirely merged together, and almost all 

 the detail lost (cf. Figs. 88 and 89). 



Exner's view of the impression produced on the insect eye of the 

 degree of rapidity of movement in any objects, viz. that it is inti- 



FiG. 88. 



Leaf of Ailanthus glandulosa, showing part taken by the different portions 

 of the compound eye in viewing it. 



Fig. 89. 



Effect produced on the retina by the leaf thus viewed. 



mately connected with the movement of the insect itself, must lead 

 to absurd conclusions. Joh. Muller's view, that insects see objects 

 only by means of the accurate perception of their illumination, is 

 the most important point in the theory of mosaic sight (that of 



