120 MENTAL EVOLUTION IN ANIMALS. 



This, therefore, we may mark off as another distinct stage in 

 the evolution of mnemonics. 



After this stage has advanced to a considerable extent, so 

 that numerous concrete and compound ideas are associated in 

 a great many chains of more or less length or number of 

 links, a sufficient body of psychological data has been fur- 

 nished to admit of the next stage of memory being reached, 

 or that of association by similarity. Professor Bain remarks : 

 " The force of contiguity strings together in the mind words 

 that have been uttered together ; the force of similarity brings 

 forward recollections from different times and circumstances 

 and connexions, and makes a new train out of many old 

 ones."* And as in these higher planes of human memory, so 

 in the lower ones of animal memory; association by similarity 

 impiies a better development of ideation than does associa- 

 tion by contiguity. 



The next and final stage of Memory is attained when 

 reflection enables the mind to localize in the past the time 

 when an event remembered took place. This is the stage of 

 memory which is called Eecollection, and occurs in all cases 

 where the mind knows that some particular association of 

 ideas has previously been formed, and is therefore able deli- 

 berately to search the memory until the particular association 

 required is brought into the light of consciousness. 



I have now given a sketch of the successive stages in the 

 evolution of Memory, drawing a line to mark off a stage 

 wherever I have been able to distinguish a place where a 

 line could be drawn. It is needless to say that here, as in all 

 similar cases, I deem these lines to be of a purely arbitrary 

 character, and introduce them only to give a general idea of 

 the upward growth of a continuously developing faculty. I 

 shall now conclude this chapter by briefly glancing at the 

 animal kingdom and the growing child with reference to the 

 evolution of Memory. 



Taking first the case of the child, I have assigned the 

 seventh week as the appropriate age at which to mark the 

 first evidence of memory in the association of ideas. I do so 

 because I have observed that this is the age at which hand- 

 fed children first recognize the feeding-bottle, i.e., an artificial 

 object without smell or other quality that can arouse any 

 ancestral instincts, and one which young infants always 



* Senses and Intellect, p. 469. 



