166 RESPONSE IN THE LIVING AND NON-LIVING 
Sometimes this process is very rapid, and 
decline. 
in any case, under continued light, the deflection falls. 
(1) The decline may nearly reach zero. If now the 
light be cut off there is a rebound towards recovery 
downwards, which carries it below zero, followed by an 
after-oscillation (fig. 108, a) 
(2) If the light be continued for a longer time, the 
decline goes on even below zero; that is to say, the 
(0) (c/ 




; pe ey 
4m 8m \l2m \6ir 

1 i rn 25, 
4 8m lem \|6m O 
1 
1 
' 
1 
' 
' 
1 
! 
‘ 
' 
‘ 
1 
1 
1 
1 
1 
1 
t 
i 
u 
Fic. 108 —Dxcuine UNDER THE ConTINUED Action or LicuT 
(a) Decline short of zero; on stoppage of light, rebound downwards to zero ; 
after-oscillation. 
(b) Decline below zero; on stoppage of light, rebound towards zero, with pre- 
liminary negative twitch. 
(c) The same, decline further down; negative twitch almost disappearing. 
response now becomes apparently negative. If, now, 
the light be stopped, there is a rebound upwards to 
recovery, with, generally speaking, a slight preliminary 
twitch downwards (fig. 108, 6, c). This rebound 
carries it back, not only to the zero position, but some- 
times beyond that position. We have here a parallel to 
the following observation of Dewar and McKendrick: 
