236 JACQUES LOEB AND HARDOLPH WASTENEYS 



Visual purple is bleached most rapidly by light of the wave 

 length of about 530 /x^t (according to Trendelenburg). Neither 

 Chlamydomonas nor the larvae of Balanus show their maximal 

 sensitiveness exactly at this point ; whether the slight deviation is 

 only due to the imperfections of the experimental method or due 

 to the fact that the photosensitive substance is not identical with 

 visual purple can not be decided on the basis of the material which 

 is at present available. 



We find likewise that those organisms which react best to the 

 blue part of the spectrum do not all have their greatest sensi- 

 tiveness in the same spot of the blue. Thus the seedlings of 

 oats are most sensitive to a region of X = 466 ix/jl, the animal 

 Eudendrium and the flagellate Euglena for a region near X = 

 460 to 490 fji/jL, while the larvae of Arenicola are. most sensitive 

 to X = 495 MM- 



