DARWINISAf 157 



mistake in basing his theory upon " Individual Differences " ; 

 but Dr. Vernon's new book having just appeared, it becomes 

 necessary to show how he confirms, though it be quite uninten- 

 tionally, the statement that individual differences do nof, as a 

 rule, help one to discover the origin of variations. 



He commences his first chapter as follows : " If a number 

 of individuals of any species be compared, it will be found that 

 they all show differences from each other either in size, shape, 

 colour, etc., . . . in fact, no two of them are exactly alike. . . . 

 These differences constitute what is known as Variation, and it 

 is into the facts of this variation, and its importance as the 

 corner-stone of the whole fabric of Evolution, that we shall 

 briefly inquire in the following pages." 



Dr. Vernon proceeds to give us illustrations of the many 

 results of observers who represent individual differences by 

 mathematical curves. 



Similar curves can be made from shots at a target ; since 

 no organ of a plant or animal ever grows absolutely like 

 another, no two leaves are alike, because there is always an 

 inequality in the forces of growth, the amount of food supply, 

 etc., etc. 



Hence Wallace is right in saying that " they rarely come 

 within the hmits of a species ". 



These observers of numerical statistics seem to have in 

 some cases overlooked i^co fundamental conditions for varia- 

 tions in a true, classifactory sense of the word ; viz., changed 

 conditions of life or the nature of the environment, and 

 hereditary constancy. 



There is no use in collecting hundreds or thousands of 

 animals, such as crabs, shrimps, etc., or heads of daisies, 

 marigolds, etc., all coming, respectively from the same locality. 



No systematist takes any notice of individual differences ; 

 because they are too slight and too inconstant. 



Variations which systematists can only recognise must have 

 more pronounced differences, and there ?nust be hereditary 

 constancy. 



