FOULING OP SHIPS' BOTTOMS 



245 



yellow, the stimulatiiig efficiency is equal to more than 50 per cent that of white 

 light; while between 530 and 545 mu-mu it is more than 90 per cent, or virtually 



PERCENTAGE 100 

 OF 90 



INDIVIDUALS 80- 

 REACTING 70 

 FILTER 60- 



WHITE 50- 



40 

 30- 

 20- 

 10- 



WAVE ! 



LENGTHS 350 



OF 

 FILTER IN 

 WILLI -MICRA ! 

 (MU-MU) 



600 



1700 



5 ^ 



ct c> ^ * o r> o OS :s S " <^ 



'■ Ti'i'ii I I' I 



FiQ. 38.— Distribution of the stimulating efficiency of equal energy values among the various parts of the spectrum for the 

 cyprid larvse of certain barnacles 



equivalent to white light. On the other hand, light of wave lengths of 700 mu-mu 

 has less than 5 per cent of the efficiency of white light, and likewise at 420 mu-mu 



A. B. C. 



I I \ 



Fig. 39. — Attachment of barnacle larvse with reference to source of illumination (indicated by arrows) 



the stimulating efficiency is very much reduced. For a more complete account of 

 these experiments see Visscher and Luce (1928). 



