COLOR VISION 349 



In later experiments Lubbock used more refined methods. 

 He had a prismatic electric-hght spectrum thrown upon a 

 nest especially prepared for the purpose. Ten different 

 experiments were made with this, the results of which were 

 similar. I shall quote one in full: 



" Professor Dewar kindly prepared for me a condensed 

 pure spectrum (showing the metallic lines) w^ith a Siemens' 

 machine, using glass lenses and a mirror to give a perpen- 

 dicular incidence when thrown on the nest. ... I arranged 

 the light and the ants as before, placing the pupae in the 

 ultra-violet, some being distinctly beyond the bright 

 thalline band. The ants began at once to remove them. 

 At first many were deposited in the violet, some, however, 

 being at once carried into the dark beyond the red. When 

 all had been removed from the ultra-violet, they directed 

 their attention to those in the violet, some being carried, 

 as before, into the dark, some into the red and yellow. 

 Again, w^hen those in the violet had all been removed, 

 they began on the pupae in the red and yellow, and car- 

 ried them also into the dark. This took nearly half an 

 hour. As I had arranged the pupae so that it might be 

 said that they were awkwardly placed, we then turned the 

 nest round, leaving the pupae otherwise as they had been 

 arranged by the ants; but the result of moving the nest 

 was to bring some of them into the violet, though most 

 were in the ultra-violet. They were, as before, all carried 

 into the dark space beyond the red in about half an hour. 



'* We then turned the glass round again, this time 

 arranging the end about the length of the spectrum be- 

 yond the end of the violet visible to our eyes. They began 

 clearing the thalline band, carrying some into the violet, but 

 the majority away further from the spectrum. In a quarter 

 of an hour the thalline band had been quite cleared; and 

 in half an hour a band beyond, and equal to the thalline 

 band, those in the violet being left untouched. After 

 the pupae in the ultra-violet portion had all been moved, 

 those in the violet were also carried away and deposited 



