IV 



EVOLUTION 



EVOLUTION has been a hard road to travel, 

 but are not all roads that lead upward more 

 or less hard? The downward roads are the easy ones 

 — the road of degeneration or devolution — no pain, 

 no struggle, no effort, only placid acquiescence. 



The sea squirt begins life as a free, active little 

 fish, a simple vertebrate with powers of locomotion; 

 but it soon takes the road of devolution instead of 

 evolution; it attaches itself to a stone, or a shell, or 

 other fixed object, loses its special sense organs 

 and the beginnings of a backbone, and becomes a 

 "mere rooted bag with a double neck." The barna- 

 cle takes the easy downward road in the same way, 

 degenerating from a free, swimming, six-legged, 

 compound-eyed creature, like a* young crab or a 

 shrimp, into a mere immovable* shellfish attached 

 to a rock or a ship-bottom. 



§ 

 The main factor in the progress of evolution is, of 

 course, the tendency to variation, and this tend- 

 ency seems to become more and more pronounced 

 as life proceeds and becomes more complex. It is 

 more pronounced in the higher forms than in the 

 lower. This fact doubtless accounts for the more 

 273 



