REPORT OF COMMISSIONERS OF INLAND FISHERIES. 249 



Description of Plate XXXIX. 



The current in every case was a continuous circular current created by a revolv- 

 ing paddle in a large canvas bag. 



Fig. 1. Shows the normal rheotactic phenomenon when no dis- 

 turbing influence is brought to bear. 



Fig. 2. Shows the effect of introducing a pencil of light so that 

 the rays proceed in an opposite direction to the current. 



Fig. 3. Shows the result when the rays proceed in the direction 

 of the current. 



Fig. 4. Shows the effect of allowing the rays to fall vertically or 

 at right angles to the direction of the current. 



Fig. 6. Shows the effect of introducing the rays at a slight angle 

 when no current is flowing in the bag. 



Fig. 7. Shows the effect of withdrawing the source of the rays 

 in a "serpentine" curve, in such a way that the direction of the rays 

 is continually changing but at every point is tangent to the curve. 



