ON INSTINCT AND REASON 67 



machinery, organs, and viscera for the performance of 

 particular and specific functions, and for nervine centralisa- 

 tion and reflex innervation, until entering the region of 

 the vertebrates we discover that the principle of centralisa- 

 tion has reached proportions in which a great nervine 

 emporium, exchange, or brain, has been evolved from 

 the upper or anterior nerve ganglia of their more 

 elementarily developed progenitors, and means arranged 

 by which the movements of their bodies can be effected 

 on determinant lines, or by the aid of reason. Necessarily, 

 in its earliest stages of evolution, reason is much overlaid 

 and affected by instinct, and hence its infant efforts are 

 often so rudimentary and meaningless as to betoken the 

 still prevalent subjugation by its ally and ancient master, 

 instinct ; the movements and activities evinced by the 

 organisms of the early vertebrate animals are therefore 

 largely dominated and determined by instinct, which is 

 yet powerful, and very little by reason, which is feeble, 

 and has not yet obtained the position of ascendency 

 which it ultimately is allowed to obtain in determining the 

 actions and shaping the destinies of its possessors. Here, 

 necessarily, where the growth of reason is yet rudimentary, 

 instinct is more trusted and obeyed than it, with the 

 result that evolutionary progress is made more automati- 

 cally secure and exact, and the way thereby prepared 

 for the advent of reason, with the prospect of its ultimate 

 ascension to the vacant throne in the mental hierarchy 

 of man himself. 



At that stage of neural evolution and mental develop- 

 ment which we have now reached, where man appears 

 on the scene, we have attained a point in our enquiry 

 into the nature of the processes involved in the production 

 and existence of instinct and reason respectively, which 

 will, we hope, enable us more fully to realise their true 

 nature and the causes of the similarities and differences 

 which characterise them, as well as some of the poten- 

 tialities and limitations belonging to them, as the great 

 guiding influences at work in determining and shaping 

 the destinies of the various species and genera possessing 

 them. 



In the above short summary we have seen, but 



