610 WOLFGANG F. EWALD 



acceleration of locomotion. Within limits, the absolute inten- 

 sity of illumination does not affect these reactions. 



2. It was found that light of different wave lengths influenced 

 these reactions in a different way. Green and yellow-green 

 have the strongest effect; blue-green, blue, yellow, violet and 

 red follow in the order named. 



3. The same order of efficiency is found, when the orienting 

 power of different parts of the spectrum is tested. The positive 

 animals collect in the green on the side near the Hght, the nega- 

 tive animals in the red and violet on the far side. 



4. The velocity with which positive animals become negative 

 is also different for different parts of the spectrum, but in a 

 different order. Balanus larvae became negative most quickly 

 in the violet and in the green, less quickly in the blue and the 

 yellow and hardly at all in the red. 



5. The ultra-violet rays have the most strongly deleterious 

 effect on the larvae. The violet rays follow next, then the green 

 and the blue, while the red rays of the intensities tested had no 

 harmful effect. 



II. Effects of temperature 



6. Increase of temperature made positive animals negative 

 and negative animals more strongly negative; decrease of tem- 

 perature made negative animals positive and positive animals 

 more strongly positive. 



///. Effects of the salts of the seawater in isotonic solutions 



7. Isotonic sodium chloride solution, pure or added to natural 

 seawater, makes negative animals positive and positive animals 

 more positive. If sufficiently in excess of the other salts, it 

 inhibits negative reaction entirely. 



8. Isotonic potassium chloride solution, added to natural sea- 

 water, acts in the same direction, though less effectively. 



9. Isotonic calcium chloride solution, added to natural sea- 

 water, makes the larvae lose their power of reaction to light 

 stimuli, causing them to swim about at random without nega- 

 tive or positive orientation. 



