dG'^ Causes and Course of Organic Evolution 



together, • compare even in feeble degree to the trunk, as a 

 medium for conveying afferent and efferent impulses. In fact 

 it may truly be said that the proboscis for the nemertean and a 

 like organ for the elephant have been the fundamental organs 

 for evolving the mentality of both groups. Composed largely 

 as it is in the elephant of muscle and nerves, these are in inti- 

 mate association and almost constant action, while they are 

 innervated by, and are sending constant environal stimulatory 

 currents to, the brain, that is placed exactly in line with the 

 base of the proboscis. So if one watch the huge impassive 

 mass of a caged elephant when confronted by a throng of ad- 

 mirers and food-contributors, except for an occasional shifting 

 of the eyes, the trunk is the centre of constantly changing 

 motion. Even when the animal is undisturbed, or is asleep, 

 the twitchings and movements of the trunk indicate its extreme 

 sensitivity. 



Is the trunk then a developmental result of brain stimuli 

 passing to the snout region, or has contact stimulus of the 

 trunk with surrounding objects gradually stimulated the nerve 

 substance to cell multiplication and increase, or have trunk 

 development and brain growth proceeded in corresponding 

 ratio? Alike on physical and physiological principles, the last 

 is the only alternative. For the chemic, thermic, — possibly 

 also electric — energy derived from food supplies is here con- 

 verted into biotic energy, that is passed into and energizes the 

 trunk. This organ is constantly reaching out proenvironally 

 to new stimulatory objects, aided more or less by the eyes, the 

 ears, or the nose-tissue. These objects affect it chemically, 

 thermally, luminously, and so start cognitic stimuli that travel 

 to the brain, there to be stored and linked up with other im- 

 pressions, or from the brain efferent responsive impulses pro- 

 ceed. By incessant action, continued in ever-increasing ratio 

 from the times of the mid-eocene onward — let us say conserva- 

 tively for two millions of years — these varied cognitic stimuli 

 and responses have been changed into higher and greatly more 

 complex cogitic acts, that constitute the "high mentality" of 

 the existing species. 



