128 GEORGE DELWIN ALLEN. 



PLATE II. 



FIG. 3. The system of spiral currents. Photograph of pan in which the water 

 has been stirred in the clockwise direction and then drops of carmine have been 

 placed on the bottom at various points about its circumference. The dark lines 

 are streaks of carmine produced by the currents and showing the direction of the 

 currents upon the bottom. 



FIG. 4. A positive reaction showing individual variation in the precision of 

 orientation. 



