120 NATURE AND LIFE. 



little beings were remarked in the red, too, a certain num- 

 ber in the blue, and some, fewer in proportion to the dis- 

 tance, in the most refrangible portions of the violet and 

 ultra-violet. For these insects, as for ourselves, the most 

 luminous part of the spectrum was also the most agreeable. 

 They behaved in it as a man would do who, if he wished to 

 read in a spectrum thrown about him, would approach the 

 yellow and avoid the violet. This proves, in the first place, 

 that these insects see all the luminous rays that we see 

 ourselves. Do they perceive the colorific and chemic rays, 

 that is to say, the ultra-red and ultra-violet ones, which do 

 not affect our retina? Bert's experiments enable us to 

 answer that they do not. That physiologist is even led to 

 assert that, with regard to light and the different rays, all 

 animals experience the same impressions that man does. 



Let us now look at the influence of light upon the 

 color of the skin in animals, noticing first the being which 

 presents the strangest peculiarities in this respect, the 

 chameleon. This animal, indeed, experiences very fre- 

 quent modifications of color in the course of the same day. 

 From Aristotle, who attributed these changes to a swell- 

 ing of the skin, and Theophrastus, who assigned fear as 

 their cause, to Wallisniri, who supposes them to result 

 from the movement of humors toward the surface of the 

 animal's body, the most different opinions have been ex- 

 pressed on this subject. Milne-Edwards, thirty years ago, 

 explained them by the successive inequalities in the pro- 

 portions of the two substances, one yellowish and the other 

 violet, which color the skin of the reptile, inequalities due 

 to the changes in volume of the very flattened cells that 

 contain these substances. Bruck, renewing these researches, 

 proves that the chameleon's colors follow from the mani- 

 fold dispersion of solar light in the colored cells, that is to 

 say, from the production of the same phenomenon remarked 

 in soap-bubbles and all very thin plates. Its colors, then, 



