212 DAPHNIAS.AND COLORS. 



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

 concludes that they peic(^ive 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. " Tous les animaux voient les rayons spectraux 

 que nous voyous." 



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

 pas. 



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

 entre les f ouvoirs eclairants des differents rayons 

 colores sont h^s memes pour eiix et pour nous." 



He also adds, "Puisque les li mites de visibilite 

 semblent etre les memes pour les animaux et pom- 

 nous, ne trouvons-nous pas 1^ une raison de plus pour 

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

 secondaire, et que la vis-ibilite tient a I'impression- 

 nabilite de I'appareil nerveux lui-meuie?" 



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 (o arrange for me, at 

 the Koyal Institution, a Sjiectrum, 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 

 Suoiety for 1881. 



