54 VITAL FORCE, INSTINCT, AND SENSAIIOX. 



a central orgau in relation to the protoplast that lives in a solitary cell. It is 

 not of course to be supposed that within a whole plant-structure, that is in the 

 community of li\-c protoplasts which constitutes an individual plant, such a con- 

 centration of stimulation could occur as is the ease with individual animals which 

 have nerve -fibres all converging into the brain; but between the sensation of 

 animals without nerves and that of plants no essential difference can exist. 



Hence we infer that there is no barrier between plants and animals. The 

 attempt to establish a boundary-line where the realm of plants ceases and the 

 animal world begins is a vain one. If we naturalists, all the same, agree to 

 separate plants and animals, we do so only because experience shows that a 

 division of labour conduces to a speedier attainment of our object. On the 

 intermediate ground where animals and plants meet, zoologists and botanists 

 encounter one another, not, however, as hostile rivals with a view to exclusive 

 possession of the field, but as colleagues with a conunon interest in the adminis- 

 tration and culti\ ation of this jointly tenanted i-egion. 



