106 Instinct and Intelligence 



these pallial or cortical nervous elements 

 gradually become developed, and ultimately 

 assume the structural and functional character 

 of what is known as the neopallium. Nerve 

 fibres can be traced from these cortical cells, as 

 well as directly from the olfactory, visual, and 

 tactile sensory organs to the basal or instinctive 

 ganglia. Consequently, we find in the brain of 

 the most primitive class of existing true verte- 

 brates nervous structures whose main function 

 it is to elaborate instinctive processes; it also 

 contains elements having a tendency to become 

 differentiated into rudimentary pallial or cor- 

 tical nervous structures, which in the higher 

 animals are indispensable for the occurrence of 

 psychical processes. 



The instinctive behaviour of a rudimentary 

 form of brain, such as that possessed by a 

 lamprey, is of a correspondingly low type. 

 This animal has a circular mouth armed with 

 numerous hard tubercles which serve as teeth, 

 by which the animal is able to hold on to the 

 body of its prey; its tongue acts like a piston 

 in its mouth, and enables the creature to draw 

 in as well as expel water through its gills, and 



