368 REFLEX ACTION, INSTINCT, AND REASON 



if any such occur in him, are adapted only to meet the needs of 

 the moment, with a man, who, in early youth, may form a plan 

 (e.g. the achievement of wealth), and pursue it undeviatingly in 

 ways remote from the end during all the varied scenes of a long 

 life. 



609. Since mind is clearly adaptive, and since it increases in 

 amplitude and complexity from the lower to the higher animals, 

 it is apparently as much a product of evolution as the function of 

 any physical organ, for example the hand. Certainly, we have 

 as much reason to suppose it is such a product to suppose that the 

 functions of the brain have undergone evolution in the same sense, in 

 the same way, and by the same means as the functions of the hand. 

 It is, in fact, a 'character' (a reaction to stimulus) of the indivi- 

 dual, which, as far as we are able to surmise, was, like other useful 

 characters, absent in remote ancestors, had its origin in variations, 

 and, passing through simple to more complex types, underwent 

 evolution (as a function) by the action of Natural Selection. 

 There is evidence that we are able by careful selection to increase 

 or decrease in any desired direction the intelligence of our 

 domesticated animals. In parasites and other animals which have 

 forsaken an active existence, mind appears to have undergone 

 retrogression through cessation of selection. Again, some animals, 

 which lead an active existence early in the individual life, but 

 which lapse into an inactive adult stage, seem to lose their minds 

 just as they lose their larval organs. In brief, mind owes its 

 existence to its utility. 



610. Various authors have supposed that, " the beginnings of 

 mental life date back from the beginnings of physical life. The 

 question of the origin of mental development thus resolves itself 

 into the question of the origin of life." * If they are right we are 



1 Wundt, Principles of Physiological Psychology, Eng. Trans., vol. i. p. 31. 

 Here Wundt is very unconvincing. We are told that " the beginnings of a 

 differentiation of mental function can, however, be found even in the protozoa. 

 . . . The only sense that is plainly functioning is the sense of touch . . . the 

 cilia with which these infusorians'are furnished . . . are . . . organs of motion. 

 They function as organs of touch, and sometimes appear sensitive to light as 

 well " (pp. 33-4). But reaction to stimulus does not necessarily imply sensation. 

 The environment of infusorians is so simple, their reactions to it so few, that 

 sensation superimposed on the reactions made by them would appear to be a 

 useless epi-phenomenon. No sensations, as far as we are aware, accompany 

 much more complex reactions in our own bodies, for example the normal move- 

 ments of our intestines. " In the compound organisms we observe a more 

 radical differentiation of mental function and its bodily substrate. The cell- 

 mass of the yolk, originally homogeneous, divides first of all into a peripheral and 

 a central layer of different structural character, while the cleavage cavity gradually 



