ANTS SENSITIVE TO ULTRA-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. ‘Tous les animaux voient les rayons spectraux 
que nous voyons.” . 
B. ‘Ils ne voient aucun de ceux que nous ne 
voyons pas.’ 
C. ‘Dans l’étendue de la région visible, les différ- 
ences entre les pouvoirs éclairants des différents rayons 
eoloriés sont les mémes pour eux et pour nous.’ 
He adds, that ‘puisque les limites de visibilités 
semblent étre les mémes pour les animaux et pour nous, 
1 Archiv. de Physiol. 1869, p. 547. 
