ii THE PLANT AND THE ANIMAL 119 



differs. Ordinarily, one of the two tendencies covers 

 or crushes down the other, but in exceptional circum 

 stances the suppressed one starts up and regains the 

 place it had lost. The mobility and consciousness of 

 the vegetable cell are not so sound asleep that they can 

 not rouse themselves when circumstances permit or 

 demand it ; and, on the other hand, the evolution of 

 the animal kingdom has always been retarded, or stopped, 

 or dragged back, by the tendency it has kept toward 

 the vegetative life. However full, however overflow 

 ing the activity of an animal species may appear, torpor 

 and unconsciousness are always lying in wait for it. It 

 keeps up its r61e only by effort, at the price of fatigue. 

 Along the route on which the animal has evolved, 

 there have been numberless shortcomings and cases of 

 decay, generally associated with parasitic habits ; they 

 are so many shuntings on to the vegetative life. Thus, 

 everything bears out the belief that vegetable and 

 animal are descended from a common ancestor which 

 united the tendencies of both in a rudimentary state. 



But the two tendencies mutually implied in this 

 rudimentary form became dissociated as they grew. 

 Hence the world of plants with its fixity and insensi 

 bility, hence the animals with their mobility and con 

 sciousness. There is no need, in order to explain this 

 dividing into two, to bring in any mysterious force. It is 

 enough to point out that the living being leans naturally 

 toward what is most convenient to it, and that vegetables 

 and animals have chosen two different kinds of con 

 venience in the way of procuring the carbon and nitrogen 

 they need. Vegetables continually and mechanically 

 draw these elements from an environment that continu 

 ally provides it. Animals, by action that is discon 

 tinuous, concentrated in certain moments, and conscious. 



