LECT. v USE OF FOREGOING FACTS 227 



variability occurs in all animals and plants, even to 

 a large extent ? Of course, if all parts of any animal 

 or plant were to vary to the extent which has been 

 shown, variability might explain the production of 

 new species ; but do they really vary to this extent 

 in any one individual or group of individuals ? 

 Certainly not, and we must admit that variability is 

 limited, and that it is not, so far as we know, sufficient 

 to create new species. The differences are not 

 numerous enough. 



What, then, is the use of the series of facts which 

 have been examined, and what do they show ? 



They provide a basis for the study of variation, 

 specific or otherwise, in showing that no species are so 

 very permanent in their structure or functions that no 

 departure from their type is possible. They form the 

 solid ground on which evolutionists stand, and 

 if this ground were missing the evolution hypo- 

 thesis would have no support at all, and would be 

 nothing more than an aerial and unfounded structure. 

 In the second place, they provide the basis and suggest 

 the methods for experimental transform ism. 



Believing as we do that transmutation or evolution 

 must have taken place under the action of natural 

 causes and influences, we consider that these causes 

 have been natural selection and environment, in pro- 

 portions which we cannot determine. But these causes 



Q 2 



