lo CHAPTERS ON EVOLUTION. 



the discussion of such a topic certain fundamental truths and propo- 

 sitions of biology therefore fall to be discussed. 



Thus fortified and prepared by these introductory details, the 

 evidences of evolution as the great process which summarises in 

 itself the forces and tendencies of living beings fall to be noted. The 

 first of these evidences is constituted by " rudimentary organs," and 

 the tale they tell of animal and plant modification. Here the curious 

 nature of these apparently useless parts is seen to be fully borne out 

 by the idea that they refer " to a former state of things," and that 

 they represent the natural, but deteriorated and vanishing remains of 

 structures once useful in the ancestors of the animals that now 

 possess them. 



The sixth chapter strikes a somewhat related key-note to that 

 touched in the preceding section. The evidence deducible from the 

 modifications which animal structures have undergone is largely in 

 favour of evolution. The structures specially selected for treatment 

 in this chapter are the tails, limbs, and lungs. It is attempted to be 

 shown that these organs illustrate in the clearest manner how adap- 

 tation to new ways of life is induced by alterations in the habits and 

 surroundings of animal forms. Incidentally, information is likewise 

 afforded respecting certain interesting aspects of the structure of 

 higher animals. 



The science of likenesses (or homology) forms the special topic 

 of the succeeding section. Herein the general deductions of 

 " homology " are discussed and illustrated from both animal and 

 vegetable worlds. The broad likenesses between animals which 

 were discussed in the third chapter, are here specialised, and the 

 natural correspondence existing between parts and organs, often of the 

 most diverse appearance, is duly dwelt upon. In its general tenor, 

 this chapter will be found to follow out the line of argument specially 

 selected in chapter sixth. 



The subject of "missing links" is treated in the eighth chapter. 

 No topic in all the wide range of evolution demands more detailed 

 treatment than that of the "links" between apparently distinct 

 groups of animals the existence of which the theory itself postulates, 

 and the necessity for which is a matter of popular notoriety. The 

 higher animals have been specially selected for treatment in this 

 chapter, not merely because the case for evolution is more likely to- 

 be duly appreciated when these forms are selected for discussion, 

 but because the evidence is overwhelmingly clear in favour of 

 evolution when the higher groups are examined, and also because 

 links in lower life are duly treated in succeeding chapters under 

 the head of " Development." 



The succeeding three chapters deal with the evidence afforded 

 by development in favour of evolution. All evolutionists may 



