EEYIEW OF THE MODERN DOCTRmE OF EYOLUTIOIT. 225 



II. THE LAWS OF EVOLUTIOIT. 



Having reviewed the reasons why the doctrine of evolution 

 should be received as truth, I desire to give attention to the laws 

 which may be made out by reference to its phenomena. Progress 

 in this direction is difficult, owing to the natural impediments in 

 the way of studying the history of the growth of living beings. 

 We will, however, commence by examining more fully the phe- 

 nomena with which we have to deal. 



It is well understood that the world of animal life is a nicely 

 adjusted equilibrium, maintained between each individual and its 

 environment. This environment exerts forces both purely physi- 

 cal, and those exercised by other animals. Animals antagonize 

 each other in procuring food, whether that food consist of vegeta- 

 tion or of other animals, but in the latter case the conflict is more 

 severe. A similar competition exists among male animals in the 

 matter of reproduction. These exhibitions of energy constitute 

 the struggle for existence, which is the daily business of the living 

 world. It is well understood that in this struggle the individuals 

 best provided with means of self-preservation necessarily survive, 

 while the weak in resources must disappear from the scene. 

 Hence those which survive must display some especial fitness for 

 existence under the circumstances of their environment, whatever 

 they may be. So the ^^ survival of the fittest" is believed to be a 

 law of evolution, and the process by which it is brought about has 

 been termed ** natural selection." The works of Darwin and 

 others have satisfied biologists that this is a vera causa. 



Before the excellence of a machine can be tested, it must exist, 

 and before man or nature selects the best, there must be at least 

 two to choose from as alternatives. Furthermore, it is exceedingly 

 improbable that the nicely adapted machinery of animals should 

 have come into existence without the operation of causes leading 

 directly to that end. The doctrines of **^ selection " and "sur- 

 vival " plainly do not reach the kernel of evolution, which is, as I 

 have long since pointed out, the question of "the origin of the 

 fittest." The omission of this problem from the discussion of 

 evolution, is to leave Hamlet out of the play to which he has 

 given the name. The law by which structures originate is one 

 thing ; those by which they are restricted, directed, or destroyed, 

 is another thing. 



There are two kinds of evolution, progressive and retrogres- 

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