XIX 



HEREDITY 



375 



ANIMALS 



Dominant Character 



Hornlessness in cattle. 



Normal short hair in rabbits 

 and guinea-pigs. 



Short tail in Manx cat (some- 

 what imperfectly domi- 

 nant). 



Normal movements in mice. 



Crest in poultry. 



Rose comb and Pea comb. 



Extra toes. 



Broodiness. 



Unbanded shell in wood- snail. 



Greyness in mouse. 



Pink eye in fruit-fly. 



Recessive Character 



Presence of horns. 

 Long " Angora " hair. 



Normal length of tail. 



Waltzing in mice. 

 Absence of crest. 

 Single comb. 

 Normal four toes. 

 Absence of this instinct. 

 Banded shell. 

 Albinism in mouse. 

 White eye in fruit-fly. 



PLANTS 



Dominant Character 



Peas : 



Tall stems. 



Yellow cotyledons. 



Brown-skinned seeds. 



Round seeds. 

 Wheat : 



Absence of awn. 



Rough and red chaff. 



Keeled glumes. 



Flinty endosperm. 



Susceptibility to rust. 

 Barley : Two-rowed ears. 

 Nettles : Markedly dentate 

 leaves. 



Recessive Character 



Dwarf stems. 

 Green cotyledons. 

 White seeds. 

 Wrinkled seeds. 



Presence of awn. 

 Smooth and white chaff. 

 Rounded glumes. 

 Floury endosperm. 

 Immunity to rust. 

 Six-rowed ears. 

 Slightly dentate leaves. 



Why one character is dominant and another recessive 

 we cannot tell, nor do we know if there is a quality 

 common to all dominant characters and a quality com- 

 mon to all recessive characters. A glance at the repre- 

 sentative list will show that there is great variety in 

 the characters which exhibit Mendelian inheritance. In 

 mankind the best illustrations arc furnished by brachy- 

 dactylism (where the fingers are all thumbs, two joints 

 instead of three), by night-blindness (a condition of the 

 eye apparently due to the absence of the visual purple), 

 and by the colour of the iris. 



