2 PRELIMINARY CONSIDERATIONS 



leaves recover from the closed and pendent condition 

 in which they are found at night, and if not dis- 

 turbed in any manner they remain erect and unfolded 

 until evening, when they again close and droop ; and 

 these alternations recur in this order so long as the 

 characteristic sensitiveness is retained. In both cases, 

 indeed, there is a manifest connexion between the 

 phenomena and certain changes in the relative 

 positions of the earth and sun, the one referring to 

 the annual, and the other to the diurnal revolution ; 

 and hence it may be argued that the vital movements 

 of the sensitive plant are due to the joint operation of 

 cosmical force, and of an innate principle which 

 belongs to the individual organism. 



The egg of the lizard, like the seed of which we 

 have spoken, exhibits no signs of development unless 

 it be quickened and fostered by external agents ; and 

 the same aid is necessary after the animal has escaped 

 from the shell. In the perfect state there is a sensi- 

 tive and intelligent principle by which the actions are 

 regulated and governed, but this does not supersede 

 the foreign powers which acted upon the egg. It is a 

 constant rule, indeed, for this animal to be active and 

 full of life in warm weather, and to hybernate in cold 

 the periods of animation and torpidity being in 

 exact correspondence with the summer and winter; 

 and it is equally constant for the same animal, when 

 in its active state, to wake throughout the day and to 



