30 Transactions. — Miscellaneous. 



himself says, entirely confirm the opinion Lord Avebury ex- 

 pressed — that there is not sufficient evidence among insects 

 of anything which can justly be called a " sense of direction." 

 In conclusion, I should like to allude to the very remark- 

 able discovery made by Lord Avebury some years ago in con- 

 nection with the limits of vision in ants — i.e., the power 

 possessed by those insects of perceiving the ultra-violet rays 

 of the spectrum, which are invisible to human eyes. This 

 fact was elicited by means of a very exhaustive series of ex- 

 periments, during which the ants were placed under variously 

 coloured glasses, and also under two distinct, though exactly 

 similarly coloured, chemical solutions, one of which intercepted 

 the ultra-violet rays, whilst the other allowed these invisible 

 rays to pass through it. The results of these numerous ex- 

 periments are very conclusive, and are recounted at length in 

 Lord Avebury's delightful book on " Ants, Bees, and Wasps." 

 I will not now repeat the details of these experiments, but the 

 following general reflections suggested by this discovery are 

 of more than passing interest, and may well conclude this 

 address : " 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 per- 

 ceive at all, appears to us as a distinct colour, it becomes prob- 

 able that these ultra-violet rays must make themselves 

 apparent to the ants as a distinct and separate colour (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 colour. At 

 any rate, as few of the colours 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 colours 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 how 

 different the world may — I was going to say must — appear to 

 other animals from what it does to us. Sound is the sensa- 

 tion produced on us when the vibrations of the air strike on 

 the drum of our ear. "When they are few the sound is deep ; 

 as they increase in number it becomes shriller and shriller ; 

 but when they reach forty thousand in a second they cease to 

 be audible. Light is the effect produced on us when waves of 

 light strike on the eye. When four hundred millions of 

 millions of vibrations of ether strike the retina m a second 

 they produce red, and as the number increases the colour 



