MULTICELLULAR ANIMALS AND COLOR 345 



green rays between 450 and 600'^'^. In the red-blue and 

 green-blue tests the intensity of the red and green was 

 twice as high as that of the blue. In the red-green test it 

 was a little more than twice as high in the red as in the 

 green. In these tests, however, the worms consistently 

 collected in the light having the higher intensity, whereas 

 in white hght the opposite was true. However, when 

 white light containing ultra-violet was contrasted with 

 white light without, but of decidedly higher intensity, the 

 great majority collected in the light having the higher 

 intensity. 



Considering the conditions of these experiments I do 

 not hesitate to conclude that blue, violet and ultra-violet 

 are more efficient in causing reactions in Lumbricus than 

 green or red. Similar conclusions are strongly supported 

 by the reactions of various other species, notably the 

 snail Limnaeus stagnalis and several insect larvae as well 

 as imagos. In numerous other instances, however, as 

 already intimated, the results are not conclusive; in these 

 it is questionable whether the quality of light has any 

 specific functions and it is impossible to say to what the 

 change in distribution is due. 



The following conclusion of Graber is undoubtedly not 

 warranted (1884, p. 245): " Als eines der allerwichtigsten 

 und interessantesten Ergebnisse meiner vergleichenden 

 Lichtgefiihl-Studien betrachte ich die Tatsache, dass die 

 leukophilen oder weissholden Tiere mit geringen Ausnahmen 

 alle blatdiehend, die leukophohen oder dunkelholden hingegen 

 rotliehend sind^ 



The results of these experiments appear to indicate that 

 in general animals which are positive in white light are 

 also positive in blue, whereas those which are negative in 

 white are negative in blue, not positive to red, as Graber's 

 conclusions would suggest. This is however not univer- 

 sally true, as the experiments on Daphnia clearly show. 



The ideas in Graber's conclusions expressed in the quo- 

 tations above and elsewhere, that animals actually perceive 



