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?”’—TuHomas 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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