122 SIE J. LUBBOCK ON THE SENSE OE COLOK 



His words are : — 



A. " Tous 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 differences entre 

 les pouvoirs eclairants des differents rayons colores sontles 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'ceil est tout a fait secondaire, et que la visibilite tient a Timpres- 

 sionnabilite de I'appareil nerveux lui-meme ? " 



These generalizations would seem to rest on a very narrow 

 foundation. I bave already attempted to sbow that the con- 

 clusion 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 embodied in the present com- 

 munication. 



Prof. Dewar was kind enough again to arrange for me a spec- 

 trum, which, by means of a mirror, was thrown onto the floor. 

 I then placed some Daphnias in a wooden trough 14 inches by 

 4 inches, and divided by cross partitions of glass into divisions, 

 so that I could isolate the parts illuminated by the different 

 colored rays. The two ends of the trough extended some- 

 what beyond the visible spectrum. I then placed fifty specimens 

 of Daphnia pules in the trough, removing the glass partitions so 

 that they could circulate freely from one end of the trough to the 

 other. Then, after scattering them equally through the water, I 

 exposed them to the light for ten minutes, after which I inserted 

 the glass partitions, and then counted the Daphnias in each divi- 

 sion. The results were as follows : — 



Number of Daphnias. 



101 183 12 



