GENESIS OF MAN, INTELLECTUALLY 



other anatomical peculiarities of man. Below 

 that minimum the whole accompanying struc- 

 ture undergoes far more than a corresponding 

 change, — even the whole change between the 

 lowest savage and the highest ape. Above that 

 minimum, all subsequent variations in quantity 

 are accompanied by no changes whatever in phy- 

 sical structure."^ Here again, though the anti- 

 thesis is a little too absolutely stated, we have 

 set before us a real distinction. Up to a cer- 

 tain point, the brain and the rest of the body 

 are alike alterable by natural selection and such 

 other agencies as may be concerned in the slow 

 modification of organisms. But when the brain 

 has reached a certain point in size and complex- 

 ity, the rest of the body ceases to change, save 

 in a few slight particulars, and the agencies con- 

 cerned in forwarding the process of evolution 

 seem to confine themselves to the brain, and 

 especially to the cerebrum, — the result being 

 marked psychical development, unattended by 

 any notable physical alteration. Here we have 

 reached a fact of prime importance. We may 

 grant to the Duke of Argyll that when those 

 eleven additional cubic inches of brain had been 

 acquired, some kind of a Rubicon had been 

 crossed, and a new state of things inaugurated. 

 What was that Rubicon ? 



The answer has been furnished by Mr. Wal- 

 ^ Duke of Argyll, Primeval Man, pp. 57—64. 



95 



