Chap. IL] MENTAL POWERS. 37 



may then be said to be degraded in character, for they are 

 no longer performed through reason or from experience. 

 But the greater number of the more complex instincts ap- 

 pear to have been gained in a wholly different manner, 

 through the natural selection of variations of simpler in- 

 stinctive actions. Such variations appear to arise from 

 the same unknown causes acting on the cerebral organiza- 

 tion, which induce slight variations or individual differ- 

 ences in other parts of the body; and these variations, 

 owing to our ignorance, are often said to arise sponta- 

 neously. We can, I think, come to no other conclusion 

 with respect to the origin of the more complex instincts, 

 when we reflect on the marvellous instincts of sterile 

 worker-ants and bees, which leave no offspring to inherit 

 the effects of experience and of modified habits. 



Although a high degree of intelligence is certainly 

 compatible with the existence of complex instincts, as we 

 see in the insects just named and in the beaver, it is not 

 improbable that they may to a certain extent interfere 

 with each other's development. Little is known about 

 the functions of the brain, but we can perceive that, as 

 the intellectual powers become highly developed, the va- 

 rious parts of the brain must be connected by the most 

 intricate channels of intercommunication ; and as a conse- 

 quence each separate part would, perhaps, tend to be- 

 come less well fitted to answer in a definite and uniform, 

 that is instinctive, manner to particular sensations or as- 

 sociations. 



I have thought this digression worth giving, because 

 we may easily underrate the mental powers of the higher 

 animals, and especially of man, when we compare their 

 actions, founded on the memory of past events, on fore- 

 sight, reason, and imagination, with exactly similar actions 

 instinctively performed by the lower animals ; in this lat- 

 ter case, the capacity of performing such actions having 



