MAN'S ARBOREAL APPRENTICESHIP 293 



It may be objected that many marsupials are 

 arboreal, and yet they do not seem to have made 

 much of their educational opportunities. But the 

 answer is that the ground-plan of the marsupial , 

 brain is different from that of placental mammals 

 and precluded great advance. As to the problem 

 whether improvement in brains brought about an 

 increasing manual dexterity, or whether bodily 

 improvements made possible a cerebral advance, 

 Professor Wood Jones gives the right answer, that 

 the two sets of improvements went hand in hand. 

 " The evolution of the free and mobile fore limb 

 in arboreal life may be likened to the production of 

 a musical instrument an instrument upon which it 

 is impossible for the animal to produce a full range , 

 of harmony, or to appreciate the psychical connota- 

 tions of this harmony, unless adequate cerebration 

 is developed coincidently." Perhaps a somewhat 

 similar answer may be given to the question that 

 confronts us at every turn: How all these adapta- 

 tions to arboreal life could arise if functional modi- 

 fications acquired by individuals are not entailed 

 as part of the inheritance of the race. From the 

 fountain of change hidden in the dark recesses of 

 the germ-cells there is a welling forth of tentatives 

 and initiatives, but it rests with the explicit organism 

 as a genuine agent to put these variations and 

 mutations to the test, for if this is not done they will 

 profit nothing, and, being born before their time, 

 will disappear unappreciated. 



