148 EVOLUTION 



of the organism counts for more than the 

 conditions. 



Changed habits, e.g. changes in the de- 

 gree of_use or disuse of a part, produce an 

 inherited effect., witness thp lighter wing- 

 bones and heavier leg-bones of the domestic 

 duck, or the enlarged udders of cows. 



Variations are often definitely correla-ted: 

 thus short-beaked pigeons have small feet; 

 hairless dogs have imperfect teeth; and 

 blue-eyed white tom-cats are deaf. JHence^ 

 ^jfTtiio 11 n f ftTiy-'Onft rhnracter will prob- 

 Tnf.' 



Although the laws of inheritance are 

 mostly unknown, it seems that probably 

 -if not nil; .characters tend to be 



herited. There is no satisfactory evidence 

 to support the popular idea that domestic 

 varieties revert to*tJie "priftrftiV N stofek ^Vhen 

 they run wild. Reversions occasionally 

 QiCCl 1 ^..? 1 ^ nrnp st^R^ 3> l or^ but there is no gen- 

 eral tendency to lose what has been gained 

 apart, of course, from breeding with wild 

 stocks, or with other domesticated ones. 



-Excet)t in bein^ less nn^'orm triinTi nfliturril 

 specie, in jjfpn diffrring morn widely in n. 

 sinprle part, and 13 K&ing fertile when crossed. 

 thfre nrp nf> well mnr^^ r|[gtinotion,^ hp- 

 twfifin our r1rmir3J>io- r^,c p 'u 



_ 

 true_species of a genus. The many breeds of 



