214 EVOLUTION OF TO-DAY. 



doubtedly its cause. Changes of conditions certainly 

 produce variations, but the changes of conditions 

 are so infinite in number and quality, that the varia- 

 tions which they produce must also be looked upon 

 as infinite. No law of variation has yet been dis- 

 covered. It is possible, and even probable, that 

 similar changes in condition should produce similar 

 variations in individuals, but we can seldom under- 

 stand why they should do so. In order that natural 

 selection can act, it is necessary that there should be 

 something to select. Now we may concede to the 

 theory that the changes of conditions are sufficient 

 to account for variation. No two animals have the 

 same surroundings, and we well know that the 

 different surroundings of animals produce their 

 effect. We may also, for the present, concede that 

 organisms have an inherent tendency to vary. If 

 these two positions be granted, there will be no lack 

 of variations, which can be selected. But these varia- 

 tions will, as a rule, be irregular and indefinite ; will 

 be usually of slight importance, occurring in any 

 direction, and confined, as a rule, to only one, or at 

 most a few individuals at a time. Now there is no 

 doubt that such variations do occur. Any one who 

 will take the trouble to examine a half a dozen in- 

 dividuals of any species, can convince himself of 

 this fact. These variations then, minute, indefinite, 

 irregular, form the foundation of Darwinism. Such 

 variations may be readily believed to be due to the 

 constantly varying conditions ; and Darwin, per- 

 ceiving them to be abundant, and unable to account 

 for more important ones, believed the natural selec- 



