DARWIN AND PALEONTOLOGY 249 



interplay. One feature has been omitted: that 

 is, that all the branches of all the phyla, with one 

 exception, show a continuous and progressive in- 

 crease in size. This increase in size is, however, 

 itself interpreted not only as a response to favor- 

 able environment, but also to the selection of he- 

 reditary variations in size due to the fact that 

 the larger quadrupeds are better able to stand 

 off the attacks of their carnivorous enemies. 



CONCLUSION 



This interpretation, finally, is seen to include 

 the cooperation of factors recognized by Buffon, 

 by Lamarck, and by Darwin, except as to the 

 transmission of acquired characters, which is left 

 in doubt. There is, however, a new principle in 

 the " mutation of Waagen " or " rectigradations 

 of Osborn," unknown to Darwin and due to 

 causes entirely unknown to us at the present time, 

 and perhaps, as already intimated, unknowable. 

 In this connection it is interesting to recall the 

 comment of Aristotle ^ on the survival-of-the- 

 fittest theory (the bracketed insertions [ ] and 

 itaKcs are our own) : — 



" What, then, hinders but that the parts in Nature 



may also thus arise [namely, according to law]. For 



instance, that the teeth should arise from necessity, the 



front teeth sharp and adapted to divide food, the 



grinders broad and adapted to breaking the food into 



pieces. 



'■ Osborn, H. P. : From the Oreeks to Darwm, 8vo, Macmillan 

 & Co., 1894, p. 56. 



