THE KANGE OP VISION AND OF HEARING. 191 



construct microscopes far more powerful than any we 

 now possess, they could not enable us to obtain by 

 direct vision any idea of the ultimate molecules of 

 matter. The smallest sphere of organic matter which 

 could be clearly defined with our most powerful micro- 

 scopes may be, in reality, very complex ; may be built 

 up of many millions of molecules, and it follows that 

 there may be an almost infinite number of structural 

 characters in organic tissues which we can at present 

 foresee no mode of examining. 



Again, it has been shown that animals hear sounds 

 which are beyond the range of our hearing, and that 

 they can perceive the ultra-violet rays, which are 

 invisible to our eyes.* 



Now, as every ray of homogeneous light which we 

 can perceive at all, appears to us as a distinct color, 

 it becomes probable that these ultra-violet rays must 

 make themselves apparent to the ants as a distinct and 

 separate color (of which we can form no idea), but as 

 different from the rest as red is from yellow, or green 

 from violet. The question also arises whether white 

 light to these insects would differ from our white light 

 in containing this additional color. At any rate, as 

 few of the colors in nature are pure, but almost all 

 arise from the combination of rays of different wave- 

 lengths, and as in such cases the visible resultant 

 would be composed not only of the rays we see, but of 

 these and the ultra-violet, it would appear that the 

 colors of objects and the general aspect of nature 

 must present to animals a very different appearance 

 from what it does to us. 



These considerations cannot but raise the reflection 

 * " Ants, Bees, and Wasps." 



