164 THE ZOOLOGIST. 
device was repeated many times during the several minutes in 
which the hawk persisted in its attack. : 
Coming next to the nature of the movements, I suggest that 
both the lower and the higher forms are imitations of the spray 
thrown up by the waves of the sea when they meet with solid 
obstruction. Several considerations warrant this view. The 
column of sea-spray and the column of Waders each describe a 
curved path in a vertical plane through the atmosphere. In 
general form and in detail the two curves have much in common. 
In both there is a quick upcast gradually slowing down, and, at 
the summit, curving over into a descent, the speed of which 
steadily increases until the movement is at an end. In both the 
upcast column looks white and solid, the descending column is 
more scattered and reflects less light. The ‘‘ reverse” of the 
Waders at the summit of their curve resembles a peculiar move- 
ment of the drops of water at the summit of the column of spray. 
As the water turns over the summit, the particles tend to slip 
quickly downwards and to one side until the arcuate movement 
is arrested with great suddenness by the force of gravity. The 
abrupt change of the strongly reflective drops of water from one 
direction of movement into another produces the sensation of a 
flash of light. This effect is similar to that excited by the 
‘reverse’? of the Waders. After the column of spray has been 
propelled upwards to a great height, the descending drops adopt 
a movement of their own, in addition to the movement of 
descent. It gives them a glittering appearance, and also slows 
the descent. These two conditions are simulated by the Waders 
during the descent of the higher form of movement. During 
the descent of high sprays the drops of water sometimes alter 
their form and appearance a second time. This occurs on a 
level with the summit of the lower spray, and takes place in- 
stantly. The drops become blurred in outline, extended hori- 
zontally, and more reflective of light—characters which are 
retained to the end of the descent. The sudden increase of the 
reflection has its counterpart in the effect produced by the 
‘reverse,’ which sometimes happens at a similar level during 
the descent of the Waders in the higher form of movement. One 
other circumstance to which I have not yet referred is certainly 
not the least remarkable, and seems to have a more important 
