The Tests of Evolution 239 



year I described a lovely rosy Chaunax, a chubby, pot- 

 bellied deep-sea fish which had its only near ally in one 

 described from the Bay of Panama, and my fish came from 

 the south coast of Cuba in a thousand fathoms of water. 



Unfortunately the lines, "Some call it Evolution, And 

 others call it God," however true they may be, savor of 

 the trite and the smug. No one who thinks and has had 

 a real chance to study modern paleontological material 

 doubts the fact of evolution, but the mystery behind it all 

 is deep and dark and as worthy of our worship, if you will, 

 as it ever was. Scientists have seen the evidence where evo- 

 lution has run riot. The dinosaurs reached a size which was 

 mechanically disadvantageous. The Irish elk proceeded to 

 produce such gigantic horns (which presumably were 

 dropped each year) that their very renovation from year 

 to year must have involved a fatal weakening of the stock, 

 which of course has long since disappeared. Cope had a 

 phrase for this process, and a good one, too. It was "super- 

 abundant growth force" — growth in a particular direction 

 until it becomes lethal. 



But what brings this force into being? Darwin provided 

 a couple of useful slogans — "sexual selection," "the struggle 

 for existence," and Spencer added "the survival of the 

 fittest." 



Each one of these explains a good deal. But let us apply 

 it, for instance, to the leaf butterfly and see just how much 

 it helps us. Metaphorically speaking, a racial stock of but- 

 terflies for its own protection starts out to become dead- 

 leaf -like. If this change were to be accomplished by natural 

 selection alone, it would be reasonable to suppose that as 



