INTRODUCTION. 9 



reserved for a separate chapter. But more than this, 

 it has been held by certain naturalists that species 

 have arisen from several distinct points, and not 

 from one. They would say that there have been a 

 number of points of origin, one for each of the sub- 

 kingdoms. But this position is hardly a tenable 

 one and is now generally abandoned. It is, of 

 course, perfectly possible that such might have been 

 the history of animals, even upon the theory of 

 evolution, but there is not the slightest evidence 

 that such was the case. On the contrary, as we 

 shall see later, the evidence is such as to apply to all 

 species alike, and if its force is admitted at all, it 

 must be admitted as linking the organic world into a 

 single unit, and not into several. The sub-kingdoms 

 are united together at the bottom, and if evolution 

 is admitted at all, it must apply to the whole organic 

 world. While, then, it is desirable to confine the 

 subject to limits where it can be investigated and 

 attested by facts, it is equally desirable to avoid the 

 other extreme and fail to see that evolution must 

 cover all organic species or none. 



Evolution is not Darwinism. 



We have now reached a conclusion as to what is 

 ordinarily meant by evolution, and such was Dar- 

 win's understanding of the term. But it must not 

 be confounded with Darwinism. Evolution is sim- 

 ply a theory as to the method by which species have 

 been introduced into the world, entirely independent 

 of any idea as to the causes which have brought about 

 their introduction. Darwinism is evolution ; but it 



