COLOURING OF STEBCOBABIUS CREPIDATUS. 373 



plain, the other lovely. This suggests a passage from one to the 

 other, and if the plain form most resembles the young bird in 

 colouring (which is my own experience), whilst the young bird 

 resembles, more than any old one, an allied plainer species, this 

 seems to make it more than likely that the passage is from the 

 plain to the lovely, and not from the lovely to the plain. Sup- 

 porting and emphasizing this, we have the absence of those 

 lance-like feathers in the tail of the young bird which give so 

 marked a character to, and add so infinitely to the grace of, the 

 old one. Of what use can this thin projection an inch or so 

 beyond the serviceable fan of the tail be to the bird ? Seeing 

 how well every other bird does without it, can we suppose it to be 

 of any service ? Its beauty, however — which one misses dread- 

 fully in the young flying bird — is apparent to anyone, and it 

 goes hand in hand with an increased and ascending scale of 

 beauty in colour. All this seems to me to point towards sexual 

 selection, since I am personally a believer in the reality of that 

 power, having never heard or read anything against it so con- 

 vincing to my mind as what Darwin has said for it, nor seen any- 

 thing that has appeared to me to be inconsistent either with his 

 facts or his arguments. 



