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CHAPTER VIII. 



VARIATION. 



FROM our observations of animals we may 

 safely conclude that no two are absolutely 

 identical. 



The differences are of three distinct 

 kinds : 



The difference among animals of admit- 

 tedly the same race. This we call 

 " Variation in expression of type " ; 

 Deviation (also among animals of the 

 same race) in one or more parts from 

 the normal type. This occurs but 

 rarely, usually in a single individual, 

 and is not hereditary. This difference 

 may be called "accidental" (? spontane- 

 ous) variation ; and 

 Persistent hereditary differences between 



two races viz., specific variation. 

 As usual in Nature, no hard line can be 

 drawn between these different classes, and 

 in some cases it may be difficult to determine 



