2O2 The Evolution Hypothesis. 



organisms evolved, it is equally certain that sameness- 

 of incident forces will produce similarity in the re- 

 sulting forms : for to affirm otherwise is to deny the 

 persistence of force. The vertebrate structure may, 

 then, be the effect of similarity of causes operating 

 in the environment and not the outcome of identity 

 of descent. 



The evolution hypothesis supposes a moment in the 

 gradual cooling of the earth, when organic matter in 

 the form of protein was produced, out of which, after 

 a vast series of minute changes, there arose particles 

 endowed with vital activities. The principle of cau- 

 sation renders it inconceivable that such dynamic 

 processes should be limited to one spot, or to one 

 particle of organic matter. Like the formation of 

 crystals of salt in all parts of the globe where water 

 containing salt in solution has evaporated, the pro- 

 duction of protein matter must have spread over the 

 whole earth, as zone after zone reached the precise 

 degree of temperature required. And so soon as pro- 

 tein was evolved, then began everywhere the further 

 changes that result in organized life. To doubt thi& 

 if the dynamic theory is true is to reject the 

 principle of causation. Now the incident forces are 

 the same, yet not absolutely the same, over the whole 

 earth. The law of gravitation operates everywhere 

 and ceaselessly. If it be of advantage in the develop- 

 ment of animal forms that the strength and flexibility 

 of a vertebrate skeleton should form the framework 



