LECTURE V 



Summary : Experimental Evolution based on the four preceding 

 Groups of Facts. These Facts illustrate at the same time its 

 Methods, which are : Change of Environment ; Use and Disuse ; 

 Natural Selection ; Sexual Selection ; and Physiological Selection. 

 These Factors of Evolution must all be subjected to Ex- 

 perimental Test in order to show what they can Effect. What is 

 wanted : A Direct Proof, which all may Perceive and Touch, of 

 one Species (or Form) giving Birth to another more or less 

 Different, and Permanent. Numerous Accessory Problems to be 

 Investigated at the same time. Scientific and Practical Import of 

 this Line of Investigation. Requirements : Farm and Laboratory ; 

 Animals and Plants ; Time ; Experiments must be able to last 

 20, 50, IOD Years or more. This Experimental Investigation 

 must and shall be performed. But who is to begin ? 



WE have thus shown that a high degree of varia- 

 bility exists among animals and plants in the natural 

 state as well as under domestication, and that through 

 the modification of environment, in part or in whole, 

 we are able to determine some changes in organisms. 

 This variability is met with in all parts of the body, 

 even in those which seem to be the most permanent. 



What does this demonstrate ? it may be asked. 

 And the objection arises : What does it matter that 



