MULTICELLULAR ANIMALS AND COLOR 347 



not show that it is more efficient than yellow or green or 

 any other rays in the spectrum. It is difficult to under- 

 stand how he could conclude that in animals '' the more 

 strongly refrangible rays of the visible spectrum are the 

 most active heliotropically, as in the case of plants," and 

 '' that the more refrangible rays have the same effect as 

 mixed rays " (1905, p. 29), after studying reactions in but 

 two different colors. 



