554 Causes and Course of Organic Evolution 



making environal contact by the antennae or by the mandibles 

 with each object passed, both of these sets of appendages being 

 close to and ancillary to the head. By steady and continued 

 use of these, in immediate connection with the brain, action 

 and reaction have caused increased perfection of both. So, as 

 compared with average insects, ants exhibit a range of activi- 

 ties that is only equaled by the more highly civilized human 

 races, and even by educated individuals of these only. Thus 

 they show^ extremely fine sense of touch, w^hile the prehensile, 

 carrying, cutting, building, digging, storing, feeding, harvest- 

 ing, fighting, slave-making, and other activities are practised. 



In connection also w^th questions taken up in later chapters, 

 it should be emphasized that many of the acts which fall 

 roughly under some one of the above categories are capable 

 of a more extended mental analysis. Thus the housing and 

 the feeding of Aphides by some ants, in order that they may 

 be milked for their excretions; the nibbling and destruction of 

 the radicle in grains that are to be stored; and numerous like 

 acts, reveal a proenvironal analysis, synthesis, and response 

 which is superior to that shown by savage races of men. 



Now if one takes account in the above list of acts performed 

 in environal relation, these result from many and often com- 

 plicated stimuli passed into the central nervous system, through 

 one or more of the circum-cephalic appendages, and which 

 are aided or guided by the optic, olfactory, or other primary 

 sense. But, while the more primitive insects have also these 

 primary senses, brain increase has proceeded but little, since 

 the active use of the accessory appendages has not been prac- 

 tised to at all so varied a degree. Strong evidence is therefore 

 again suggested that brain increase and brain complexity pro- 

 ceed pari passu, with increasingly varied and active stimuli 

 from without, that are passed in through actively movable 

 appendages accessory to the brain. 



lUit even stronger evidence is got when we compare the 

 brain of those ants which have evolved three grades of indi- 

 vidual, namely the most active or worker ants, the more pas- 

 sive and sedentary or female ants, and the least intelligent or 



