INSTINCT AND INTELLIGENCE. 655 



the ultimate cause of force, this relation lies outside the domain of 

 science. 



But, admitting this chasm which cannot be bridged admitting 

 the distinctness of psychology and physiology, a distinctness far 

 greater than exists between any other two departments of science 

 still there can be no doubt that the changes in the brain and in the 

 mind correspond with each other in the strictest manner. There can 

 be no doubt that we have here two parallel series running side by 

 side with corresponding terms, and that every change in the terms 

 of one series is associated with a change in the corresponding terms 

 of the other series. Whichsoever we take as cause, and whichsoever 

 as effect, the correspondence is undoubted. This much seems certain, 

 and this is sufficient to show that a knowledge of the terms of one 

 series must throw light on the order of succession in the terms of the 

 other series. In a word, physiology^ as the simpler and more funda- 

 mental science, must form the only true basis of a scientific psychology. 



Again, as anatomy only became scientific by becoming compara- 

 tive anatomy, i. e., by the study of the strtccture of organisms in their 

 relation to each other, or as connected by the law of evolution ; as 

 physiology, too, only became really scientific by becoming comparative 

 physiology; i. e., by tracing the gradual evolution of organic func- 

 tions j even so psychology can never assume the rank of 9, science 

 until it becomes comparative psychology ; i. e., until it adopts the 

 comparative method, until it studies the difierent grades and kinds 

 of mentality in their relation to each other, and connects them all by 

 the law of evolution. 



So much I have thought it necessary to say in order to show the 

 importance of my subject, and its close connection with physiology. 

 I now pass on to the subject itself. 



It is well known that many of the lower animals, especially certain 

 species of insects, perform acts perfectly adapted to accomplish re- 

 sults, and that without previous experience and without instruction. 

 Often the results attained are of a very complex character ; results 

 which could not be attained by ourselves except by the exercise of 

 high intelligence, aided by much experience. The extraordinary 

 capacity by which these results are reached with such unerring cer- 

 tainty is called instinct. 



I need hardly refer you to examples: You are all familiar with the 

 wonderful instinct of the common honey-bee ; their organized com- 

 munities with perfect division of labor, the precision with which they 

 make their honey-cells on perfect mathematical principles, the honors 

 paid to their queen, their care of her eggs, their wise distribution of 

 food to the larvae, both its quality and quantity, and the form and 

 size of the containing cells being varied according to the function and 

 even to some extent determining the character of the perfect insect, 

 whether drone, or queen, or worker. You are already familiar with 



