CHAPTER XI 

 INTELLIGENCE IN THE LOWER VERTEBRATES 



"To the minnow every cranny and pebble, every quality and 

 accident of its little native creek may have become familiar; but 

 does the minnow understand the ocean tides?" THOMAS CARLYLE. 



If an extra mundane observer were ignorant of the evolu- 

 tion of the vertebrates beyond the Silurian or the Devonian 

 epochs it is doubtful if he would pick out these animals as 

 the ones destined to surpass all others in psychic develop- 

 ment. The numerous species of highly organized cepha- 

 lopods that thronged the seas, the trilobites with their 

 highly developed organs of vision, the gigantic eurypterids 

 that crawled over the bottom of the shallow oceans, the 

 crustaceans, the terrestrial arachnids and the rapidly 

 evolving group of insects might all have been regarded as 

 having as much promise of future psychic development as the 

 back-boned " winners of life's race." And most of the 

 branches of the vertebrate tree really developed no further 

 than their invertebrate competitors. From among the 

 diverging branches of this phylum one only contained the 

 stock that led to the mammals and culminated in man. 



A comparative anatomist looking back upon the course of 

 evolution might have said: The vertebrates were obviously 

 the forms with the most promising psychological future. 

 Many of these ancient forms doubtless possessed a cerebral 

 cortex, a sort of appendix to the central nervous system, 

 whose especial business it is to take care of the establishment 

 of associations. The opportunity was open to them through 

 the increase in size and complexity of the association centers 



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