THE EVOLUTION OF THE MIND. 435 



ficient unto itself. It is independent and free, but it is at the same 

 time unspecialized and ineffective. Its career offers no scope for 

 volition, for a single life unit can not control the elements which sur- 

 round it. It is the sport of the wind and the wave. But the recog- 

 nition of self and non-self, which in one form or another is the attri- 

 bute of all life, is not wanting among the protozoa. Some of them 

 develop this sense to a large degree. It is said that among the 

 rhizopods are those whose appendages or pseudopodia are at once 

 cast off if they come in contact with the appendages of another of 

 the same species. This recognition of self and non-self is not intel- 

 lect, but it is homologous with the impulses on which in the higher 

 types personality depends. 



All sensation has reference to action. If a creature is not to act, 

 it can not feel. Wherever motion exists there is some sensitiveness 

 to external conditions, and this is of the nature of mind. In a com- 

 pound organism the nature and position of the sensorium or mind 

 center depend on what it has to do, or rather on what were the 

 duties the same structure had to perform in the life of the creature's 

 ancestors. 



A plant may be defined as a sessile animal. It is an organic 

 colony of cells, with the power of motion but not that of locomotion. 

 The plant draws its nourishment from inorganic Nature from air 

 and water. Its life is not conditioned on a search for food, or on the 

 movement of the body as a whole. 



The plant searches for food by a movement of the feeding parts 

 alone. In the process of growth, as Darwin has shown, the tips of 

 the branches and roots are in constant motion. This movement is 

 in a spiral squirm. It is only an exaggeration of the same action 

 in the tendrils of the growing vine. The course of the squirming 

 rootlet may be deflected from a regular spiral by the presence of 

 water. The moving branchlets will turn toward the sun. The 

 region of sensation in the plant and the point of growth are identi- 

 cal, because this is the only part that needs to move. The tender 

 tip is the plant's brain. If locomotion were in question, the plant 

 would need to be differently constructed. It would demand the 

 mechanism of the animal. The nerve, brain, and muscle of the 

 plant are all represented by the tender growing cells of the moving 

 tips. The plant is touched by moisture or sunlight. It " thinks " 

 of them, and in so doing the cells that are touched and " think " are 

 turned toward the source of the stimulus. The function of the 

 brain, therefore, in some sense exists in the tree, but there is no need 

 in the tree for a specialized sensorium. 



The many-celled animals, from the lowest to the highest, bear 

 in their organization some relation to locomotion. The animal feeds 



