INTRODUCTION xxxiii 



nothing to guide us, in that direction, but the skins of existing 

 animals. 



There is, however, some evidence which would tend to make us 

 suspect that teeth may be liable to sudden changes, owing to con- 

 traction of the jaws. Teeth, like other bones, it would appear, are 

 subject to fusion or to dissociation, as the case may be. And the 

 writer on Seals in the Royal Natural History quotes an interesting 

 example of dissociation in teeth, which I have quoted more fully 

 in another place, as I think it very instructive, and the inference to 

 to be drawn from it important. 



The doctrine of evolution has replaced every other doctrine of 

 creation, owing to the undeniable support that existing facts give 

 it. This being unstintedly admitted by all modern scientists, and 

 by many modern theologians also, there remains only to account, 

 in some way, for the appearance on this earth of the innumerable 

 creatures we see, including man himself, by the method of 

 evolution. 



Lower down in the scale of life, beyond a certain stage, we 

 cannot go, in this investigation, because breaks occur which are at 

 present in no way filled up. Whether the gaps may or may not 

 be filled up at some future period no one living can say. 



The evolution of the structure of one kind of animal from 

 another has been made clear enough, but the evolution of the 

 coloration of one kind of animal from another has not been made 

 sufficiently clear. Probably this feature in evolution has been 

 neglected, because it offered difficulties which perhaps looked like 

 puzzles. It is this feature of evolution which I have tried to make 

 clear in some of the following pages. With regard to drawing 

 conclusions, Professor Huxley x remarks : 



' What in fact lay at the foundation of all Zadig's arguments 



1 'On the method of Zadig,' Science and Hebrew Tradition, pp. 7 and 8. 



C 



