■MULTICELLULAR ANIMALS AND COLOR 337 



to enter the slit. The organisms were therefore positive 

 in all colors; the reactions however were more rapid in 

 the yellow and green than in other parts of the spectrum. 

 Bert says (1869), " II fut facile de remarquer, qu'elles 

 accouraient beaucoup plus rapidement au jaune ou au 

 vert qu'a toute autre couleur."^ 



When the opaque screen was removed so as to expose 

 the daphnias to the entire spectrum at once, most of them 

 collected in the yellow and green. Bert was of the opinion 

 that the distribution of effect in the spectrum is the same 

 in Daphnia as it is in man, and he concluded that the col- 

 lection of Daphnia in the yellow and green part of the 

 spectrum and the great activity in these colors is not 

 due to color vision, but to the fact that the light intensity 

 in this part of the spectrum is higher than elsewhere. 

 He was of the opinion that light affects these animals 

 much as it does the human being, with reference to 

 brightness, that the yellow for them as for man is the 

 brightest and consequently the most effective part of the 

 spectrum. 



Results similar to those recorded by Bert were obtained 

 by Merejkowsky (1881) on Dias longiremis and larvae of 

 Balanus, by Lubbock (1881) on Daphnia, and by Yerkes 

 (1900) on Simocephalus. 



Merejkowsky states that he exposed Dias longiremis and 

 Balanus larvae in light of different colors but of equal 

 brightness and found no evidence of preference. The valid- 

 ity of these results is, however, questionable, since it is by 

 no means certain that the brightness of the different colors 

 used in these experiments was actually equal. 



3. Lubbock's Experiments on Daphnia 



Lubbock's experimental methods and results are far 

 more convincing than those of Merejkowsky. He pub- 

 lished his interesting observations on Daphnia in the 



^ Taken from Loeb (1905, p. 9). Page in original not given by Loeb. 



