INTRODUCTION xxvii 



five digits, instead of the many digits of the Ichthyosaur form. I 

 think no one has ever credited these extinct animals with having 

 been first land animals which took to a water life. There is, more- 

 over, some evidence in favour of considering them mammals. 



Professors and authors would seem to have stereotyped on our 

 brain the words * normality/ ' anomaly,' ' monstrosity,' giving them 

 certain arbitrary meanings. They perhaps may have thought that 

 they had settled all matters regarding creation, as far as such 

 phenomena were concerned. But let us imagine that anomalies 

 and monstrosities may possibly have been ' factors in the origin of 

 species.' Then we begin to see that the method of creation will 

 appear under a somewhat different aspect from what books and 

 professors have taught us. 



Under the heading of * Monstrosities,' I have discussed these 

 particular phenomena, and have endeavoured to show that what 

 we call monstrosities may have been more frequent factors in 

 modifying the structure of animals than has been supposed. 



As the whole arm can be suppressed in one birth, so, I imagine, 

 could the Archeopteryx have had its long tail shortened to the 

 little stump of the modern bird in one birth. The objection to 

 such a sudden transformation seems to rest only in the minds of 

 those who have worked up into an unalterable dogma the notion 

 that modifications in organisms are brought about solely by slow 

 degrees. This dogma may possess no unalterability outside the 

 brain of scientists. 



It might be said, if this were so, the long tail of the Archeo- 

 pteryx would have revealed itself sometime by a sudden reversion. 

 But reversions in some organisms either rarely happen, or do not 

 happen at all, and if they do happen, sometimes they may escape 

 notice. 



For instance, no botanist doubts that the leaf of the orange and 



