EVIDENCES OF EVOLUTION 47 



obscure. A practical study of the species of 

 plants and animals, and of the way one 

 category of classification includes those be- 

 neath it classes, orders; orders, families; 

 families, genera; genera, species; species, 

 varieties; and varieties, individuals gives us 

 " an impression of affiliation " which we do 

 not get from a classification of rocks or other 

 inanimate objects. It is impossible not to 

 feel in biological classification the suggestion 

 of pedigrees and heraldry. 



VESTIGIAL STRUCTURES. Both in plants 

 and animals it is common to find minute and 

 more or less useless representatives of organs 

 which are well developed and functional in 

 related forms. It is impossible for us nowadays 

 to keep from calling these structures vestigial 

 (a better term than rudimentary, which should 

 be kept for what is incipient), and from regard- 

 ing them as the tell-tale evidences of remote 

 ancestry. Darwin compared them to the 

 unsounded letters in many words, such as the 

 " o " in leopard, the " b " in doubt, the " g " 

 in reign, which are quite functionless, but tell 

 us something about the history of these words. 

 Every one is familiar with the numerous 

 functionless flaps and buttons in clothing 

 which once had a meaning they have now 

 lost. Similar " vestigial structures " or " sur- 



