CHAPTER I 



THE ANIMAL KINGDOM 



THE doctrine of descent with modification teaches 

 us that just as the numerous varieties of any of our 

 domestic animals have certainly been derived from 

 one or perhaps a few wild ancestral species, so the 

 various forms of wild animals now existing are the 

 modified descendants of pre-existing forms, which, if 

 we could follow them back into the uttermost recesses 

 of the past, would exhibit less and less diversity of 

 structure. Finally we would arrive at comparatively 

 few and generalized types from which have sprung 

 all the endless forms of animal life in past and present 

 times. 



Although in imagination we can retrace this 

 evolution of animal life to its very simplest origins, 

 yet when we come to replace our imaginary scheme 

 by a series of animal types which are known to exist 

 or to have existed in past times, it is found that 

 there are very serious gaps in our knowledge, and 

 that so far from being able to reconstruct the com- 

 plete ancestral history of the animal kingdom in an 



S. A. K. 1 



