212 DAPHNIAS AND COLORS. 



ing to the genus Daphnia (Fig, 118), from which he 

 concludes that tliey perceive all the colors known to us, 

 being, however, especially 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 justi- 

 fied in concluding, from the experience of two species 

 — Man and Daphnia — that the limits of vision would 

 be the same in all cases. 



His words are — 



1. " Tons les animaux voient les rayons spectraux 

 que nous voyons." 



2. " lis ne voient aucun de ceux que nous ne voyons 

 pas." 



3. " Dans I'etendue de la region visible, les differences 

 entre les pouvoirs eclairants des differents rayons 

 colores sent les memes pour eux et pour nous." 



He also adds, "Puisque les limites de visibilite 

 semblent etre les memes pour les animaux et pour 

 nous, ne trouvons-nous pas la une raison de plus pour 

 supposer que le role des milieux de I'oeil est tout a fait 

 secondaire, et que la visibilite tient a I'impression- 

 nabilite de Tappareil nerveux lui-meme ? " 



These generalizations would seem to rest on a very 

 narrow foundation. I have already attempted to show 

 that the conclusion does not appear to hold good in the 

 case of ants ; and I determined, therefore, to make some 

 experiments myself on Daphnias, the results of which 

 are here embodied.* 



Professor Dewar was kind enough to arrange for me, at 

 the Koyal Institution, a spectrum, which, by means of a 

 mirror, was thrown on to the floor. I then placed some 



* These observations were published in the Journal of the Linnean 

 bwiety for 1881. 



