THE CAUSE OF VARIATION 



BY ARCHER D. WILDE 



It is a trite observation, said Darwin, that no two creatures 

 in nature are alike, and fifty years of Darwinism have not made 

 it less so. I will not therefore trouble my readers with any 

 considerable expansion of the theme, but rather adopt it as a 

 postulate, not only that there are no two creatures alike, but 

 also that if two of the likest possible, for example two animals 

 of the same litter, or two cells derived by fission from one, 

 are compared, they differ in every particular. And not only so, 

 but no two parts of the same creature are alike. Like as they 

 seem to the eye, two hairs of the same animal, placed under 

 a microscope, are at once seen to differ ; and drawings of 

 cellular structures seen under high microscopic powers show 

 that no two contiguous cells resemble each other exactly. 

 Throughout organic nature general similarity is accompanied 

 by unlikeness in detail. As between parents and their offspring, 

 as between the several offspring of the same parents, and more 

 widely as between the members of any generation of any kind 

 of plant or animal, these differences are called variations, and 

 much labour has been expended in attempts to account for their 

 origin. These I pass over at present, but one hypothetical 

 question regarding such individual differences I wish to ask, in 

 order to answer it in my own way. If by microscopes of con- 

 tinually increasing power we could examine the structure not 

 only of the cells, but also of their component plasms or 

 materials, and again the structure of the units of which these 

 materials might be found to consist, where ultimately should we 

 find these differences end ? Not long ago the answer would, 

 I suppose, have been, " In the chemical molecules at all events, 

 if not before reaching them, will be found units absolutely alike 

 in all respects." Recent discoveries in physics have however 

 now given grounds for the belief that not even the atoms of 

 the same element are exactly alike, for even apart from internal 

 motion they may be in different stages of a slow disintegration. 



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