356 ORIGIN OF SPECIES 



not these birds their front limbs in this precise intermediate 

 state of "neither true arms nor true wings" ? Yet these birds 

 hold their place victoriously in the battle for life; for they 

 exist in infinite numbers and of many kinds. I do not sup- 

 pose that we here see the real transitional grades through 

 which the wings of birds have passed; but what special diffi- 

 culty is there in believing that it might profit the modified 

 descendants of the penguin, first to become enabled to flap 

 along the surface of the sea like the logger-headed duck, and 

 ultimately to rise from its surface and glide through the air? 

 I will now give a few examples to illustrate the foregoing 

 remarks, and to show how liable we are to error in supposing 

 that whole groups of species have suddenly been produced. 

 Even in so short an interval as that between the first and 

 second editions of Pictet's great work on Palaeontology, pub- 

 lished in 1844-46 and 1853-57, the conclusions on the first ap- 

 pearance and disappearance of several groups of animals 

 have been considerably modified; and a third edition would 

 require still further changes. I may recall the well-known 

 fact that in geological treatises, published not many years 

 ago, mammals were always spoken of as having abruptly 

 come in at the commencement of the tertiary series. And 

 now one of the richest known accumulations of fossil mam- 

 mals belongs to the middle of the secondary series ; and true 

 mammals have been discovered in the new red sandstone at 

 . nearly the commencement of this great series. Cuvier used 

 to urge that no monkey occurred in any tertiary stratum ; but 

 now extinct species have been discovered in India, South 

 America, and in Europe, as far back as the miocene stage. 

 Had it not been for the rare accident of the preservation of 

 footsteps in the new red sandstone of the United States, who 

 would have ventured to suppose that no less than at least 

 thirty different bird-like animals, some of gigantic size, existed 

 during that period? Not a fragment of bone has been dis- 

 covered in these beds. Not long ago, palaeontologists main- 

 tained that the whole class of birds came suddenly into ex- 

 istence during the eocene period; but now we know, on the 

 authority of Professor Owen, that a bird certainly lived dur- 

 ing the deposition of the upper greensand ; and still more re- 

 cently, that strange bird, the Archeopteryx, with a long 



