SPECTRAL COLOR AND STIMULATION 523 



either in the negative or in the positive state, is not what would 

 be expected in organisms with color- vision. The relation be- 

 tween color and stimulation is of the same order in all of the fif- 

 teen species studied as it is in color-blind human beings, and in 

 one of the former (blowfly larvae) it is in fairly close agreement 

 with that of the latter. 



The lowest forms in which color-vision has been clearly es- 

 tablished are, in my opinion, honey bees. Both Lubbock ('95) 

 and Frisch ('14) have shown fairly conclusively that these in- 

 sects can be trained, in gathering honey, to select any one of a 

 considerable number of different colors regardless of their lu- 

 minous intensity. The conclusion of Frisch and Kupelwieser 

 ('13, p.' 552) that Daphnia has a sense of color (Farbensinn) is 

 in my opinion not well founded. These authors demonstrated 

 that under certain conditions Daphnia is positive in red, yellow 

 and green, and negative in blue-green, blue and violet, i.e., that 

 change from any of the former to any of the latter has the same 

 effect as an increase in luminous intensity; and that a change in 

 the opposite direction has the same effect as a decrease in lumi- 

 nous intensity. This seems to indicate merely that these two 

 groups of colors are antagonistic in their effect, just as has been 

 found to be true for similar groups in their effect on certain 

 photochemical reactions and on the reactions of some other 

 organisms (Mast, '11, pp. 310, 335). 



Loeb and Wasteneys ('16) conclude that the relation between 

 wave-length and reactions is the same in animals as it is in plants 

 and that there are two different 'Hypes of photosensitive sub- 

 stances" in both. Neither of these conclusions is well founded. 

 The first conclusion is based largely upon the fact that the rela- 

 tion mentioned above is not the same for all plants, just as it 

 is not the same for all animals. But it would be quite as logical 

 to conclude the opposite, for in some plants the shorter wave- 

 lengths are relatively more efficient as stimulating agents than 

 they are in any animals (see table 15), and in none of the plants 

 is the entire visible spectrum effective, nor are there any in which 

 the reactions depend upon the wave-length to such an extent as 

 they do in those animals which have color-vision. 



