150 EVOLUTION 



own generation. Unconscious selection, 

 \hich results from every one tyyii^g to 

 possess and breed t.liP V>pst j n rK^ii Q 1 g "i'a 



The accumulation of 



change which man effects explains why we 

 so often cannot recognize the wild parent 

 stocks of our cultivated plants, while its 

 absence in countries inhabited by uncivilized 

 man explains why these never yield plants 

 worth immediate culture, Mflfl ?s pow er f 

 i-s facilitated by keeping large num- 

 rSj ifi wl^jfch v^yiations are mQf$ fckely to 

 occur. Facility in preventing crosses \^ 

 plso <** -p f ^'rtiflinf >A i e.g. in the case of pigeons 

 as contrasted with cats; some species are, 

 however, less variable than others, e.g. the 

 goose. 



iRIATION. UNDER NATURAL CONDITIONS^ 



f^f'Vta-' '^^^^^ , * i '*ii *^ * ' 



inerences arise even in the 



l ! hence they afford material for 

 jiatural selection to act rm 



precisely as they would for human selection. 

 (It may be that genera with large num- 

 bers of slightly different species e.g. rose, 

 bramble and hawkweed owe their protean 

 character to their variations being of no 

 service or disservice, and consequently not 

 being acted on by natural selection,). In 

 determining whether groups of similar forms 



