AUTS SENSITIVE TO ULTEA-VIOLET RAYS. 219 



This result is very striking. It appears to show that 

 though to our eyes the bisulphide of carbon is absolutely 

 transparent, while the chrome alum and chromium chlo- 

 ride are very dark, to the ants, on the contrary, the 

 former appears to intercept more light than a layer of 

 the latter, which to our eyes appears dark green. 



The only experiments hitherto made with the view 

 of determining the limits of vision of animals have 

 been some by Prof. Paul Bert ' on a small fresh-water 

 crustacean belonging to the genus Daphnia, from 

 which he concludes that they perceive all the colours 

 known to us, being, however, specially sensitive to the 

 yellow and green, and that their limits of vision are 

 the same as ours. 



Nay, he even goes further than this, and feels 

 justified in concluding from the experience of two 

 widely divergent species — Man and Daphnia—that 

 the limits of vision would be the same in all cases. 



His words are — 



A. 'Tons les animaux voient les rayons spectraux 

 que nous voyons.' 



B. 'lis ne voient aucun de ceux que nous ne 

 voyons pas.' 



C. ' Dans I'etendue de la region visible, les differ- 

 ences entre les pouvoirs eelairants des differents rayons 

 eolories sont les mSmes pour eux et pour nous.' 



He adds, that 'puisque les limites de visibilites 

 gemblent Stre les mSmes pour les animaux et pour nous, 



' Arehiv. de Phytiol. 1869, p. 547. 



