34 CHAPTERS ON EVOLUTION. 



possesses them. The useless teeth of whales represent organs once 

 well developed in the ancestors of our existing toothless cetaceans ; 

 and when we find in our horse rudiments of two toes, we expect that 

 that single-toed animal is descended from a three-toed race. Is 

 such an idea probable ? may be asked. If we visit Yale College, in 

 America, and observe the array of fossil horses there displayed, 

 we shall be able to trace the evolution of the horse in time, from not 

 only three-toed, but four-toed and five-toed ancestors. There, placed 

 in a graduated series, is the proof that evolution is a stable fact. No 

 " missing links " require to be supplied in the series of Yale College : 

 and those who can maintain, in the face of such an array of testimony, 

 that evolution is an impossibility and development a myth, may be 

 regarded as possessing a hardness of heart against honest conviction, 

 compared with which the Egyptian obstinacy against which Moses 

 declaimed and Aaron battled, is mildness indeed. 



Homology, or the " science of likenesses," again, teaches us that 

 when organs are built upon the same type, like the feet of marsupials 

 or the limbs of all vertebrates, from the arm of man to the wing of the 

 bird and the breast-fin of the fish, they must have had a common 

 origin. The true nature of organs and parts in animals and plants 

 is only discoverable after a careful study and comparison of their 

 structure and affinities as declared by homology. 



Such are a few of the aids to biological study which the modern 

 naturalist has at his command. Under the light and countenance of 

 evolution, every new fact fits sooner or later into an appropriate 

 niche in the biological fabric. No one fact remains isolated and 

 distinct, as in days of old, but all our knowledge of the past and 

 present of living beings tends to supply us with a rational under- 

 standing of their origin and progress towards their existing structure 

 and position in nature. 



Evolution thus takes its stand on the rational interpretation of 

 the facts of nature. Its reasonable aspect presents its strongest 

 claim to support : its rational explanation of former mysteries com- 

 mends it to the unbiassed truth-seeker as the key to the former 

 mysteries and inexplicable problems of the past. Founding its data 

 upon observed facts, the evolution theory holds that the living species 

 of this world are in a state of constant change and variation. It 

 maintains that animals and plants are produced in greater numbers 

 than can obtain the necessaries of life. It postulates, what observa- 

 tion confirms the operation of a " struggle for existence," in which 

 the weakest forms (which are those that do not vary) go to the wall, 

 whilst the strong (those that do vary) survive. It holds that Nature 

 thus appears to set a premium on variation, that she encourages 

 change in species, and that firstly new varieties, then new races, and 

 lastly new species, are thus produced by the modification of the old. 



