206 SIB, J. LUBBOCK ON THE SENSE OE COLOU 



I believe, then, that in my previous experiments the yellow 

 liglit was too brilliant for tbem ; and the Ibilowing experiments 

 seem to show that, when sufficiently diifused, they prefer yellow 

 to white light. 



M. Merejkowski, however, denies to the Crustacea any sense . 

 of color whatever. His experiments were made with larvae of 

 Balaiiiis and with a marine Copepod, Bias longiremis. These, if 

 I understand him correctly, have given identical results. He 

 considers that they perceive all the luminous rays, and can distin- 

 guish very slight differences of intensity ; but that they do not 

 distinguish between different colors. He sums up his observa- 

 tions as follows : — 



" II resulte de ces experiences que ce qui agit sur les Crus- 

 taces, ce n'est point la qualite de la lumiere, c'est exclusivemeiit 

 sa quantite. Autrement dit, les Crustaces inferieurs ont la per- 

 ception de toute onde lumineuse et de toutes les differences, meme 

 tres legeres, dans son intensite ; mais ils ne sont point capables 

 de distinguer la nature des ondes, de differentes couleurs. lis 

 distinguent tres bien I'inteusite des vibrations etherees, leur 

 amplitude, mais point leur nombre. H y a done, dans le mode 

 de perception de la lumiere, une grande difference entre les Crus- 

 taces inferieurs et I'Homme, et meme entre eux et les Fourmis ; 

 tandis que nous voyons les differentes couleurs etleurs differentes 

 intensites, les Crustaces inferieurs ne voient qu'une seule couleur 

 dans ses differentes variations d'intensite. Nous percevons des 

 couleurs comme couleurs ; ils ne les percoient que comme 

 lumiere"*. 



It is by no means easy to decide such a question absolutely ; 

 but the subject is of much interest, and I have made some further 

 experiments, which perhaps I may be permitted to lay before the 

 Society. 



Prof. Dewar most kindly arranged the apparatus for me again. 

 He prepared a normal diffraction-spectrum, produced by a Euther- 

 furd grating with 17,000 lines to the inch ; the spectrum of the 

 first order was thrown on the trough. lu this case the distribu- 

 tion of luminous intensity has been shown to be uniform on each 

 side of the line having the mean wave-length, i. e. a little above the 

 line D in the yellowish green. 



I placed the centre of the trough at the brightest part of the 



* ' Les Crustaces inferieurs distiuguent-ils les couleurs?' Par M. C. Merej- 



