The Relation of Organic to Mental Evolution. 263 



It is probable that, throughout the vegetable kingdom, 

 evolution is in the merely organic phaSe: If there be 

 consciousHess^associated with the life of plants, there is no 

 evidence of its being a factor in the process of develop- 

 ment. It is not what we have before termed effective 

 consciousness. The lowestani mals fall under the same 

 category ; but where the n f ne is to be drawn in the animal 

 kingdom, between those in which consciousness, if present, 

 is inoperative, and those in which it is effective, who can 

 say with any certainty ? The first requisite is to findjionie 

 criterion which shall be availa ble J px- the purpo se of dis- 

 tinguishing tn^~caseTlnwhich consciousness is operative 

 from those in which it is inoperative. Such__a criterion is 

 the exercise of choice. But we must be careful, in our 

 application of the criterion, to grasp what is essential to 

 an act of choice. Invariable reaction in one way to one 

 kind of stimulus and in anot]igx--way- to another kind of 

 stimulus is regarded by M. Binet* as evidence__of choice. 

 " If we hold to what observation directly teaches us," he 

 says, " the choice may be said to consist in the following 

 acts : When an animalcule perceives certain kinds of sub- 

 stances, and particularly those substances which serve it as 

 customary food, it invariably goes through the same move- 

 ment, which consists of an act of prehension; but when 

 the substance touched, seen, or collided with, as the case 

 may be, is of another kind, the micro-organism does not go 

 through this act." I cannot agree that this is either satis- 

 factory or sufficient. Many inorganic substances, those 

 on the sensitive film of a photographic plate, for example, 

 do as much as this. If, in accordance with Pfeffer's 

 interesting observations, the spermatozoids of a fern are 

 attracted by malic acid and malates, crowding into a tube 

 which contains this substance, there is here no conclusive 



* " The Psychic Life Micro-Organisms." Eng. Trans, pp. 62, 63. 



